James K. Polk

James Knox Polk (November 2, 1795 – June 15, 1849) was the 11th President of the United States (1845–1849). Polk was born in Mecklenburg County, North Carolina. He later lived in and represented Tennessee. A Democrat, Polk served as the 17th Speaker of the House of Representatives (1835–1839) and Governor of Tennessee (1839–1841). Polk was the surprise (dark horse) candidate for president in 1844, defeating Henry Clay of the rival Whig Party by promising to annex Texas. Polk was a leader of Jacksonian Democracy during the Second Party System.

Polk was the last strong pre–Civil War president, and he is the earliest of whom there are surviving photographs taken during a term in office. He is noted for his foreign policy successes. He threatened war with Britain over the issue of which nation owned the Oregon Country, then backed away and split the ownership of the region with Britain. When Mexico rejected American annexation of Texas, Polk led the nation to a sweeping victory in the Mexican-American War, which gave the United States most of its present Southwest. He secured passage of the Walker tariff of 1846, which had low rates that pleased his native South, and he established a treasury system that lasted until 1913.

Polk oversaw the opening of the U.S. Naval Academy and the Smithsonian Institution, the groundbreaking for the Washington Monument, and the issuance of the first postage stamps in the United States. He promised to serve only one term and did not run for reelection. He died of cholera three months after his term ended.

Scholars have ranked him favorably on the list of greatest presidents for his ability to set an agenda and achieve all of it. Polk has been called the "least known consequential president" of the United States.

Early life
James Knox Polk, the first of ten children, was born on November 2, 1795 in a farmhouse (possibly a log cabin) in what is now Pineville, North Carolina in Mecklenburg County, just outside Charlotte. His father, Samuel Polk, was a slaveholder, successful farmer and surveyor of Scots-Irish descent. His mother, Jane Polk (née Knox), was a descendant of a brother of the Scottish religious reformer John Knox. She named her firstborn after her father James Knox. Like most early Scots-Irish settlers in the North Carolina mountains, the Knox and Polk families were Presbyterian. While Jane remained a devout Presbyterian her entire life, Samuel (whose father, Ezekiel Polk, was a deist) rejected dogmatic Presbyterianism. When the parents took James to church to be baptized, the father Samuel refused to declare his belief in Christianity, and the minister refused to baptize the child. In 1803, most of Polk's relatives moved to the Duck River area in what is now Maury County, Middle Tennessee; Polk's family waited until 1806 to follow. The family grew prosperous, with Samuel Polk turning to land speculation and becoming a county judge.

Polk was home schooled. His health was problematic and in 1812 his pain became so unbearable that he was taken to Dr. Ephraim McDowell of Danville, Kentucky, who operated to remove urinary stones. Polk was awake during the operation with nothing but brandy available for anesthetic, but it was successful. The surgery may have left Polk sterile, as he did not sire any children.

When Polk recovered, his father offered to bring him into the mercantile business, but Polk refused. In July 1813, Polk enrolled at the Zion Church near his home. A year later he attended an academy in Murfreesboro, where he may have met his future wife, Sarah Childress. At Murfreesboro, Polk proved a promising student. In January 1816, he transferred and was admitted into the University of North Carolina as a second-semester sophomore. The Polks had connections with the university, then a small school of about 80 students: Sam Polk was their land agent for Tennessee, and his cousin, William Polk, was a trustee. While there, Polk joined the Dialectic Society where he regularly took part in debates and learned the art of oratory. His roommate William Dunn Moseley later became the first governor of Florida. Polk graduated with honors in May 1818. The University later named the lower quad on its main campus, Polk Place.

After graduation, Polk traveled to Nashville to study law under renowned Nashville trial attorney Felix Grundy. Grundy became Polk's first mentor. On September 20, 1819, Polk, with Grundy's endorsement, was elected clerk for the Tennessee State Senate. Polk was reelected as clerk in 1821 without opposition, and would continue to serve until 1822. Polk was admitted to the bar in June 1820 and his first case was to defend his father against a public fighting charge, and secure his release for a one dollar fine. Polk's practice was successful as there were many cases arising from debts after the Panic of 1819.

Early political career
In 1822 Polk joined the Tennessee militia as a captain in the cavalry regiment of the 5th Brigade. He was later appointed a colonel on the staff of Governor William Carroll, and was afterwards often referred to or addressed by his military title. Polk's oratory became popular, earning him the nickname "Napoleon of the Stump." In 1822 Polk resigned his position as clerk to run his successful campaign for the Tennessee state legislature in 1823, in which he defeated incumbent William Yancey, becoming the new representative of Maury County. In October 1823 Polk voted for Andrew Jackson to become the next United States Senator from Tennessee. Jackson won and from then on Polk was a firm supporter of Jackson. Polk courted Sarah Childress, and they married on January 1, 1824 in Murfreesboro. Polk was then 28, and Sarah was 20 years old. They had no children. During Polk's political career, Sarah assisted her husband with his speeches, gave him advice on policy matters and played an active role in his campaigns. An old story told that Andrew Jackson had encouraged their romance when they began to court.

In 1824, Jackson ran for President but was defeated. Though Jackson had won the popular vote, neither he nor any of the other candidates (John Quincy Adams, Henry Clay, and William H. Crawford) had won a majority of the electoral vote. The House of Representatives then had to select the verdict; Clay, who had received the least amount of electoral votes and dropped from the ballot, supported Adams. Clay's support proved to be the deciding factor in the House and Adams was elected President. Adams then offered Clay a position in the Cabinet as Secretary of State.

In 1825, Polk ran for the United States House of Representatives for the Tennessee's 6th congressional district. Polk vigorously campaigned in the district. Polk was so active that Sarah began to worry about his health. During the campaign, Polk's opponents said that at the age of 29 Polk was too young for a spot in the House, but he won the election and took his seat in Congress. When Polk arrived in Washington, D.C. he roomed in Benjamin Burch's boarding house with some other Tennessee representatives, including Samuel Houston. Polk made his first major speech on March 13, 1826, in which he said that the Electoral College should be abolished and that the President should be elected by the popular vote. After Congress went into recess in the summer of 1826, Polk returned to Tennessee to see Sarah, and when Congress met again in the autumn, Polk returned to Washington with Sarah. In 1827 Polk was reelected to Congress. In 1828, Jackson ran for President again and during the campaign Polk and Jackson corresponded, with Polk giving Jackson advice on his campaign. With Jackson's victory in the election Polk began to support the administration's position in Congress. During this time, Polk continued to be reelected in the House. In August 1833, after being elected to this fifth term, Polk became the chair of the House Ways and Means Committee.

Speaker of the House
In June 1834, Speaker of the House Andrew Stevenson resigned, leaving the spot for speaker open. Polk ran against fellow Tennessean John Bell for Speaker, and, after ten ballots, Bell won. However, in 1835, Polk ran against Bell for Speaker again and won.

Polk worked for Jackson's policies as speaker, and Van Buren's when he succeeded Jackson in 1837; he appointed committees with Democratic chairs and majorities, including the New York radical C. C. Cambreleng as Chair of the Ways and Means Committee, although he maintained the facade of traditional bipartisanship. The two major issues during Polk's speakership were slavery and the economy, after the Panic of 1837. Van Buren and Polk faced pressure to rescind the Specie Circular, an act that had been signed by Jackson to boost the economy. The act required that payment for government lands be in gold and silver. However, with support from Polk and his cabinet, Van Buren chose to stick with the Specie Circular.

Polk attempted to make a more orderly house. He never challenged anyone to a duel no matter how much they insulted his honor as was customary then. Polk also issued the gag rule on petitions from abolitionists.

Polk remains the only president who served as Speaker of the House.

Governor of Tennessee
In 1838, the political situation in Tennessee—where, in 1835, Democrats had lost the governorship for the first time in their party's history—persuaded Polk to return to help the party at home. Leaving Congress in 1839, Polk became a candidate in the Tennessee gubernatorial election, defeating the incumbent Whig, Newton Cannon by about 2,500 votes, out of about 105,000.

Polk's three major programs during his governorship; regulating state banks, implementing state internal improvements, and improving education all did not get approval by the legislature. In the presidential election of 1840, Van Buren was overwhelmingly defeated by a popular Whig, William Henry Harrison. Polk received one electoral vote from Tennessee for Vice President in the election. Polk lost his own reelection to James C. Jones, in 1841, by 3,243 votes. He challenged Jones in 1843, campaigning across the state and publicly debating against Jones, but was defeated again, this time by a slightly greater margin of 3,833 votes.

Election of 1844


Polk initially hoped to be nominated for vice president at the Democratic convention, which began on May 27, 1844. The leading contender for the presidential nomination was former President Martin Van Buren, who wanted to stop the expansion of slavery. Other candidates included James Buchanan, General Lewis Cass, Cave Johnson, John C. Calhoun, and Levi Woodbury. The primary point of political contention involved the Republic of Texas, which, after declaring independence from Mexico in 1836, had asked to join the United States, but was refused by Washington. Van Buren opposed the annexation but in doing so lost the support of many Democrats, including former President Andrew Jackson, who still had much influence. Van Buren won a simple majority on the convention's first ballot but did not attain the two-thirds supermajority required for nomination. When it became clear after another six ballots that Van Buren would not win the required majority, Polk emerged as a "dark horse" candidate. After an indecisive eighth ballot, the convention unanimously nominated Polk.

Before the convention, Jackson told Polk that he was his favorite for the nomination of the Democratic Party. Even with this support, Polk instructed his managers at the convention to support Van Buren if he could win the nomination. This assured that if a deadlocked convention occurred, initial supporters of Van Buren would pick Polk as a compromise candidate for the Democrats. In the end, this is exactly what happened as a result of Polk's support of westward expansion.

When advised of his nomination, Polk replied: "It has been well observed that the office of President of the United States should neither be sought nor declined. I have never sought it, nor should I feel at liberty to decline it, if conferred upon me by the voluntary suffrages of my fellow citizens." Because the Democratic Party was splintered into bitter factions, Polk promised to serve only one term if elected, hoping that his disappointed rival Democrats would unite behind him with the knowledge that another candidate would be chosen in four years.

Polk's Whig opponent in the 1844 presidential election was Henry Clay of Kentucky. (Incumbent Whig President John Tyler—a former Democrat—had become estranged from the Whigs and was not nominated for a second term.) The annexation of Texas, which was at the forefront during the Democratic Convention, again dominated the campaign. Polk was a strong proponent of immediate annexation, while Clay seemed more equivocal and vacillating.

Another campaign issue, also related to westward expansion, involved the Oregon Country, then under the joint occupation of the United States and the United Kingdom. The Democrats had championed the cause of expansion, informally linking the controversial Texas annexation issue with a claim to the entire Oregon Country, thus appealing to both Northern and Southern expansionists. (The slogan "Fifty-four Forty or Fight", often incorrectly attributed to the 1844 election, did not appear until later; see Oregon boundary dispute.) Polk's consistent support for westward expansion—what Democrats would later call "Manifest Destiny"—likely played an important role in his victory, as his opponent Clay hedged his position.

In the election, Polk and his running mate, George M. Dallas, won in the South and West, while Clay drew support in the Northeast. Polk lost both his birth state, North Carolina, and his state of residence, Tennessee, the most recent successful presidential candidate to do so. However, he won New York, where Clay lost votes to the antislavery Liberty Party candidate James G. Birney. Also contributing to Polk's victory was the support of new immigrant voters, who opposed the Whigs' policies. Polk won the popular vote by a margin of about 39,000 out of 2.6 million, and took the Electoral College with 170 votes to Clay's 105. Polk won 15 states, while Clay won 11.

Presidency (1845–1849)
When he took office on March 4, 1845, Polk, at 49, became the youngest man at the time to assume the presidency. According to a story told decades later by George Bancroft, Polk set four clearly defined goals for his administration:
 * Reestablish the Independent Treasury System.
 * Reduce tariffs.
 * Acquire some or all of Oregon Country.
 * Acquire California and New Mexico from Mexico.

Pledged to serve only one term, he accomplished all these objectives in just four years. By linking acquisition of new lands in Oregon (with no slavery) and Texas (with slavery), he hoped to satisfy both North and South.

During his presidency James K. Polk was known as "Young Hickory", an allusion to his mentor Andrew Jackson, and "Napoleon of the Stump" for his speaking skills.

Fiscal policy
In 1846, Congress approved the Walker Tariff (named after Robert J. Walker, the Secretary of the Treasury), which represented a substantial reduction of the high Whig-backed Tariff of 1842. The new law abandoned ad valorem tariffs and set rates independent of the monetary value of the product. Polk's actions were popular in the South and West; however, they were despised by many protectionists in Pennsylvania.

In 1846, Polk approved a law restoring the Independent Treasury System, under which government funds were held in the Treasury and not in banks or other financial institutions. This established independent treasury deposit offices, separate from private or state banks, to receive all government funds.

Rivers and Harbors Veto
Congress passed the Rivers and Harbors Bill in 1846 to provide $500,000 to improve rivers and harbors, but Polk vetoed the bill. It would have provided for federally funded internal improvements on small harbors. Polk believed that this was unconstitutional because the bill unfairly favored particular areas, including ports which had no foreign trade. Polk believed that these problems were local and not national. Polk feared that passing the Rivers and Harbors Bill would encourage legislators to compete for favors for their home districts – a type of corruption that would spell doom to the virtue of the republic. In this regard he followed his hero Andrew Jackson, who had vetoed the Maysville Road Bill in 1830 on similar grounds.

Slavery


During his presidency, many abolitionists harshly criticized him as an instrument of the "Slave Power", and claimed that spreading slavery was the reason he supported annexing Texas and later war with Mexico. Polk stated in his diary that he believed slavery could not exist in the territories won from Mexico, but refused to endorse the Wilmot Proviso that would forbid it there. Polk argued instead for extending the Missouri Compromise line to the Pacific Ocean, which would prohibit the expansion of slavery above 36° 30' west of Missouri, but allow it below that line if approved by eligible voters in the territory. William Dusinberre has argued that Polk's diary, which he kept during his presidency, was written for later publication, and does not represent Polk's policy.

Polk was a slaveholder for his entire life. His father, Samuel Polk, had left Polk more than 8,000 acres (32 km²) of land, and divided about 53 slaves to his widow and children after he died. James inherited twenty of his father's slaves, either directly or from deceased brothers. In 1831, he became an absentee cotton planter, sending slaves to clear plantation land that his father had left him near Somerville, Tennessee. Four years later Polk sold his Somerville plantation and, together with his brother-in-law, bought 920 acres (3.7 km²) of land, a cotton plantation near Coffeeville, Mississippi. He ran this plantation for the rest of his life, eventually taking it over completely from his brother-in-law. Polk rarely sold slaves, although once he became President and could better afford it, he bought more. Polk's will stipulated that their slaves were to be freed after his wife Sarah had died. However, the 1863 Emancipation Proclamation and the 1865 Thirteenth Amendment to the United States Constitution freed all remaining slaves in rebel states long before the death of his wife in 1891.

Foreign policy
Polk strongly supported expansion. Democrats believed that opening up more land for yeoman farmers was critical for the success of republican virtue. (See Manifest Destiny.) Like most Southerners, he supported the annexation of Texas. To balance the interests of North and South, he wanted to acquire the Oregon Country (present-day Oregon, Washington, Idaho, and British Columbia) as well. He sought to purchase California, which Mexico had neglected.

Oregon territory


Polk put heavy pressure on Britain to resolve the Oregon boundary dispute. Since 1818, the territory had been under the joint occupation and control of the United Kingdom and the United States. Previous U.S. administrations had offered to divide the region along the 49th parallel, which was not acceptable to Britain, as they had commercial interests along the Columbia River. Although the Democratic platform asserted a claim to the entire region, Polk was willing to compromise. When the British again refused to accept the 49th parallel boundary proposal, Polk broke off negotiations and returned to the Democratic platform "All Oregon" demand (which called for all of Oregon up to the 54-40 line that marked the southern boundary of Russian Alaska). "54-40 or fight!" now became a popular rallying cry among Democrats

Polk wanted territory, not war, so he compromised with the British Foreign Secretary, Lord Aberdeen. The Oregon Treaty of 1846 divided the Oregon Country along the 49th parallel, the original American proposal. Although there were many who still clamored for the entire territory, the treaty was approved by the Senate. By settling for the 49th parallel, Polk angered many midwestern Democrats. Many of these Democrats believed that Polk had always wanted the boundary at the 49th, and that he had fooled them into believing he wanted it at the 54th parallel. The portion of Oregon territory acquired by the United States later formed the states of Washington, Oregon, and Idaho, and parts of the states of Montana and Wyoming.

Texas
Upon hearing of Polk's election to office, Tyler urged Congress to pass a joint resolution admitting Texas to the Union; Congress complied on February 28, 1845. Texas promptly accepted the offer and officially became a state on December 29, 1845. The annexation angered Mexico, which had lost Texas in 1836. Mexican politicians had repeatedly warned that annexation would lead to war. Nonetheless, just days after the resolution passed Congress, Polk declared in his inaugural address that only Texas and the United States would decide whether to annex.

Mexican-American War


After the Texas annexation, Polk turned his attention to California, hoping to acquire the territory from Mexico before any European nation did so. The main interest was San Francisco Bay as an access point for trade with Asia. In 1845, he sent diplomat John Slidell to Mexico to purchase California and New Mexico for $24–30 million. Slidell's arrival caused political turmoil in Mexico after word leaked out that he was there to purchase additional territory and not to offer compensation for the loss of Texas. The Mexicans refused to receive Slidell, citing a technical problem with his credentials. In January 1846, to increase pressure on Mexico to negotiate, Polk sent troops under General Zachary Taylor into the area between the Nueces River and the Rio Grande—territory that was claimed by both the U.S. and Mexico.

Slidell returned to Washington in May 1846, having been rebuffed by the Mexican government. Polk regarded this treatment of his diplomat as an insult and an "ample cause of war", and he prepared to ask Congress for a declaration of war. Meanwhile Taylor crossed the Rio Grande and briefly occupied Matamoros, Tamaulipas. Taylor continued to blockade ships from entering the port of Matamoros. Mere days before Polk intended to make his request to Congress, he received word that Mexican forces had crossed the Rio Grande area and killed eleven American soldiers. Polk then made this the casus belli, and in a message to Congress on May 11, 1846, he stated that Mexico had "invaded our territory and shed American blood upon the American soil."

Some Whigs, such as Abraham Lincoln, challenged Polk's version of events, but Congress overwhelmingly approved the declaration of war. Many Whigs feared that opposition would cost them politically by casting themselves as unpatriotic for not supporting the war effort.

In the House, antislavery Whigs led by John Quincy Adams voted against the war; among Democrats, Senator John C. Calhoun was the most notable opponent of the declaration.



Military action
Polk selected the top generals and set the military strategy of the war. By the summer of 1846, American forces under General Stephen W. Kearny had captured New Mexico. Meanwhile, Army captain John C. Frémont led settlers in northern California to overthrow the Mexican garrison in Sonoma (in the Bear Flag Revolt). General Zachary Taylor, at the same time, was having success on the Rio Grande, although Polk did not reinforce his troops there. The United States also negotiated a secret arrangement with Antonio López de Santa Anna, the Mexican general and dictator who had been overthrown in 1844. Santa Anna agreed that, if given safe passage into Mexico, he would attempt to persuade those in power to sell California and New Mexico to the United States. Once he reached Mexico, however, he reneged on his agreement, declared himself President, and tried to drive the American invaders back. Santa Anna's efforts, however, were in vain, as Generals Taylor and Winfield Scott destroyed all resistance. Scott captured Mexico City in September 1847, and Taylor won a series of victories in northern Mexico. Even after these battles, Mexico did not surrender until 1848, when it agreed to peace terms set out by Polk.

Peace: the Treaty of Guadalupe Hidalgo
Polk sent diplomat Nicholas Trist to negotiate with the Mexicans. Lack of progress prompted the President to order Trist to return to the United States, but the diplomat ignored the instructions and stayed in Mexico to continue bargaining. Trist successfully negotiated the Treaty of Guadalupe Hidalgo in 1848, which Polk agreed to ratify, ignoring calls from Democrats who demanded that all Mexico be annexed. The treaty added 1.2 million square miles (3.1 million square kilometers) of territory to the United States; Mexico's size was halved, while that of the United States increased by a third. California, Nevada, Utah, most of Arizona, and parts of New Mexico, Colorado and Wyoming were all included in the Mexican Cession. The treaty also recognized the annexation of Texas and acknowledged American control over the disputed territory between the Nueces River and the Rio Grande. Mexico, in turn, received $15 million. The war claimed fewer than 20,000 American lives but over 50,000 Mexican ones. It may have cost the United States $100 million. Finally, the Wilmot Proviso injected the issue of slavery in the new territories, even though Polk had insisted to Congress and in his diary that this had never been a war goal.

The treaty, however, needed ratification by the Senate. In March 1848, the Whigs, who had been so opposed to Polk's policy, suddenly changed position. Two-thirds of the Whigs voted for Polk's treaty. This ended the war and legalized the acquisition of the territories.

The war had serious consequences for Polk and the Democrats. It gave the Whig Party a unifying message of denouncing the war as an immoral act of aggression carried out through abuse of power by the president. In the 1848 election, however, the Whigs nominated General Zachary Taylor, a war hero, and celebrated his victories. Taylor refused to criticize Polk. As a result of the strain of managing the war effort directly and in close detail, Polk's health markedly declined toward the end of his presidency.

Cuba
In mid-1848, President Polk authorized his ambassador to Spain, Romulus Mitchell Saunders, to negotiate the purchase of Cuba and offer Spain up to $100 million, an astounding sum at the time for one territory, equal to $ in present day terms. Cuba was close to the United States and had slavery, so the idea appealed to Southerners but was unwelcome in the North. However, Spain was still making huge profits in Cuba (notably in sugar, molasses, rum, and tobacco), and thus the Spanish government rejected Saunders' overtures.

Department of the Interior
One of Polk's last acts as President was to sign the bill creating the Department of the Interior (March 3, 1849). This was the first new cabinet position created since the early days of the Republic. Polk had misgivings about the federal government usurping power over public lands from the states; however, the delivery of the legislation on his last full day in office gave him no time to find constitutional grounds for a veto, or to draft a sufficient veto message, so Polk signed the bill.

Supreme Court
Polk appointed the following Justices to the U.S. Supreme Court:

Woodbury was from New Hampshire, and Grier from Pennsylvania. Polk also nominated George W. Woodward of Pennsylvania in 1846, but the United States Senate rejected the nomination.

Other judicial appointments
Polk appointed eight other federal judges, one to the United States Circuit Court of the District of Columbia, and seven to various United States district courts.

Congress
29th Congress (March 4, 1845 – March 4, 1847)
 * Senate: 31 Democrats, 31 Whigs, 1 Other (President Pro Tempore – Willie P. Mangum (Whig-NC), Ambrose H. Servier (D-AR), and David R. Atchison (D-MO))
 * House: 143 Democrats, 77 Whigs, 6 Others (Speaker – John W. Davis of Indiana)

30th Congress (March 4, 1847 – March 4, 1849)
 * Senate: 36 Democrats, 21 Whigs, 1 Other (President Pro Tempore – David R. Atchison (D-MO))
 * House: 115 Whigs, 108 Democrats, 4 Others (Speaker – Robert C. Winthrop of Massachusetts)

States admitted to the Union

 * Texas – December 29, 1845
 * Iowa – December 28, 1846
 * Wisconsin – May 29, 1848

Post-presidency
Polk's time in the White House took its toll on his health. Full of enthusiasm and vigor when he entered office, Polk left on March 4, 1849, exhausted by his years of public service. He lost weight and had deep lines on his face and dark circles under his eyes. He is believed to have contracted cholera in New Orleans, Louisiana, on a goodwill tour of the South after leaving the White House. He died at his new home, Polk Place, in Nashville, Tennessee, at 3:15 pm on June 15, 1849, three months after leaving office. He was buried on the grounds of Polk Place. Polk's last words illustrate his devotion to his wife: "I love you, Sarah. For all eternity, I love you." She lived at Polk Place for over forty years after his death. She died on August 14, 1891. Polk was also survived by his mother, Jane Knox Polk, who died on January 11, 1852.

Polk had the shortest retirement of all Presidents at 103 days. He was the youngest former president to die in retirement at the age of 53. Along with George Washington, Andrew Johnson, Chester Arthur, Calvin Coolidge, and Lyndon Johnson he is one of six presidents to have died while his direct successor was in office. He and his wife are buried in a tomb on the grounds of the Tennessee State Capitol in Nashville, Tennessee. The tomb was moved to this location from their downtown Nashville mansion, Polk Place, in 1893.

Reputation
Polk's historic reputation was largely formed by the attacks made on him in his own time; the Whigs claimed that he was drawn from a well-deserved obscurity; Senator Tom Corwin of Ohio remarked "James K. Polk, of Tennessee? After that, who is safe?" The Republican historians of the nineteenth century inherited this view. Polk was a compromise between the Democrats of the North, like David Wilmot and Silas Wright, and the plantation owners who were led by John C. Calhoun; the northern Democrats thought that when they did not get their way, it was because he was the tool of the slaveholders, and the conservatives of the South insisted that he was the tool of the northern Democrats. These views were long reflected in the historical literature, until Arthur M. Schlesinger, Jr and Bernard De Voto argued that Polk was nobody's tool, but set his own goals and achieved them.

Polk is now recognized, not only as the strongest president between Jackson and Lincoln, but the president who made the United States a coast-to-coast nation. When historians began ranking the presidents in 1948, Polk ranked 10th in Arthur M. Schlesinger’s poll. and has subsequently ranked 8th in Schlesinger’s 1962 poll, 11th in the Riders-McIver Poll (1996), 11th in the most recent Siena Poll (2002), 9th in the most recent Wall Street Journal Poll (2005), and 12th in the latest C-Span Poll (2009).

Polk biographers over the years have sized up the magnitude of Polk’s achievements and his legacy, particularly his two most recent. “There are three key reasons why James K. Polk deserves recognition as a significant and influential American president,” Walter Borneman wrote. “First, Polk accomplished the objectives of his presidential term as he defined them; second, he was the most decisive chief executive before the Civil War; and third, he greatly expanded the executive power of the presidency, particularly its war powers, its role as commander-in-chief, and its oversight of the executive branch." President Harry S. Truman summarized this view by saying that Polk was "a great president. Said what he intended to do and did it."

While Polk’s legacy thus takes many forms, the most outstanding is the map of the continental United States, whose landmass he increased by a third. “To look at that map,” Robert Merry concluded, “and to take in the western and southwestern expanse included in it, is to see the magnitude of Polk’s presidential accomplishments.”

Nevertheless, Polk's aggressive expansionism has been criticized on ethical grounds. He believed in "Manifest Destiny" even more than most did. Referencing the Mexican-American War, General Ulysses S. Grant stated that "I was bitterly opposed to the [Texas annexation], and to this day regard the war, which resulted, as one of the most unjust ever waged by a stronger against a weaker nation. It was an instance of a republic following the bad example of European monarchies, in not considering justice in their desire to acquire additional territory." Whig politicians, including Abraham Lincoln and John Quincy Adams, contended that the Texas Annexation and the Mexican Cession enhanced the pro-slavery factions of the United States. Unsatisfactory conditions pertaining to the status of slavery in the territories acquired during the Polk administration led to the Compromise of 1850, one of the primary factors in the establishment of the Republican Party and later the beginning of the American Civil War.

Humorously, Sam Houston is said to have observed that Polk was "a victim of the use of water as a beverage".