Jack of the United States

The jack of the United States of America is a maritime flag representing United States nationality flown on the jackstaff in the bow of American vessels. The U.S. Navy is a prime user of jacks, but they are also used by ships of the U.S. Coast Guard, Military Sealift Command, National Oceanic and Atmospheric Administration, and other governmental entities. "The jack is flown on the bow (front) of a ship and the ensign is flown on the stern (rear) of a ship when anchored or moored. Once under way, the ensign is flown from the main mast."

History
The primary jack design until September 11, 2002 was the blue canton with stars (the "union") from the U.S. national ensign. Since September 2002, the U.S. Navy has made use of the so-called First Navy Jack. However, the standard U.S. jack (i.e., 50 white stars on a blue field) continues to be used as the jack by vessels of the U.S. Coast Guard, the Military Sealift Command, and NOAA, to name but a few federal agencies. The standard 50-star jack continues to be used by U.S. civilian ships and by U.S. yachts as well. The blue, starred jack is referred to as the Union Jack, not to be confused with the British Union Jack of the same name. Like the ensign, the number of stars on the jack has increased with each state admitted into the union. Rules for flying the jack are similar to the national ensign, except that the jack is only worn at the bow when the ship is anchored, made fast or alongside.

Since September 11, 2002, the U.S. Navy has instead flown the First Navy Jack, a flag bearing 13 red and white stripes, a rattlesnake and the motto "DONT TREAD ON ME" [sic], coming from the first jacks supposedly used by the U.S. Navy during the Revolutionary War. It is flown from the jackstaff from 08:00 to sunset while U.S. Navy ships are moored or at anchor. It is required to be the same size as the union of the ensign being flown from the stern of the ship. It is also flown from the yardarm during a general court-martial or court of inquiry. During times when the ensign is at half mast, the jack is also at half mast. The jack is hoisted smartly and lowered ceremoniously in the same manner as the ensign, however the jack is not dipped when the ensign is dipped.

Some exceptions to the use of the Union Jack have occurred in the case of the U.S. Navy, the most prominent being the use of the First Navy Jack by the U.S. Navy in honor of the country's Bicentennial and subsequently. On June 3, 1999, the Secretary of the Navy authorized the flying of the Submarine Centennial Jack aboard U.S. Navy submarines and sub tenders during the year 2000.