Jared Mansfield

Jared Mansfield (1759 – February 3, 1830) was an American mathematician and surveyor. His career was shaped by two interventions by President Thomas Jefferson. In 1801 Jefferson appointed Mansfield as Professor at the newly founded United States Military Academy at West Point. Again at Jefferson's appointment, Mansfield served as the Surveyor General of the United States from 1803 to 1812, charged with extending the survey of United States land in the Northwest Territory.

Mansfield was born in New Haven, Connecticut, son of a sea captain, Stephen Mansfield. He graduated from Yale in 1777, and taught in New Haven and Philadelphia. In 1800 he married Elizabeth Phipps, daughter of an American Naval Officer. In 1801 he had printed some scientific papers titled Essays Mathematical and Physical, which were brought to Jefferson's attention by Senator Abraham Baldwin. Jefferson appointed Mansfield captain of engineers, so he might become a professor at West Point. After moving to West Point, Mansfield was appointed Surveyor General in Summer of 1803. Jefferson was dissatisfied with the performance of Rufus Putnam, whose surveys in the Congress Lands of Ohio were poorly executed. Putnam was also a Federalist. In 1801, the position had been offered to Andrew Ellicott by Jefferson, but he refused, because he was upset at slow pay for work he had done for the Federal Government. Mansfield's Essays included sections on determining longitude and latitude, which would be useful in improving precision in surveying. Jefferson made a recess appointment, which was confirmed by the Senate November 15, 1803. He was told to "survey Ohio and lands north of the Ohio River", with later extensions to Indiana Territory and Illinois Territory.

Mansfield and his family moved to Marietta, Ohio (1803-1805), Ludlow Station (1805-1809) and near Cincinnati (1809-1812). Under Mansfield's direction the survey was continued down the Ohio River, with grids laid out northward from the river, thus dividing the territory into rectangular townships. Mansfield is credited with "considerable scientific ability and high standards of workmanship." He laid out baselines and Meridians astronomically, adapting principles of celestial navigation to surveying, which Ellicott and others had used to extend the Mason-Dixon Line decades earlier. Among his deputies were Thomas Worthington, Lewis Cass, and Ethan Allen Brown.

Jonathan Williams, Superintendent of the U.S. Military Academy sent Mansfield a letter March 20, 1809, "...your rank in the Corps doubtless settled, and I wish you were here to take direction of the Academy." The War of 1812 in the West made surveying difficult. Mansfield returned to West Point in 1814 as Professor of Mathematics and Natural and Experimental Philosophy, continuing in this position until his retirement in 1828. He never was to direct the Academy. He and his wife moved back to Cincinnati, and he died February 3, 1830 while visiting New Haven.

He arranged for Thomas Jefferson to sit at Monticello for the painter Thomas Sully, and the resulting full-length portrait now hangs in the USMA Museum.

The city of Mansfield, Ohio is named for Jared Mansfield.

He was father of author Edward Deering Mansfield.