Jack of the United States

United States of America

Jack flown by U.S. naval vessels
Name	The First Navy Jack
Proportion	1:2
Adopted	September 11, 2002
Design	13 horizontal stripes of alternating red and white, charged with a rattlesnake and inscribed on the lowest white stripe: "DONT TREAD ON ME".
Jack flown by other U.S. federal and civilian vessels. Was used as the U.S. Navy's jack prior to September 11, 2002.
Name	Union Jack
Proportion	10:7
Adopted	July 4, 1960
Design	50 white stars on a blue field in 9 rows, alternating between 6 and 5 stars.

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 that are moored or anchored. The U.S. Navy is a prime user of jacks for its warships and auxiliaries, but they are also used by ships of the U.S. Coast Guard, the predominantly civilian-manned replenishment and support ships of the U.S. Navy's Military Sealift Command, the ships of the National Oceanic and Atmospheric Administration, and other U.S. 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."

For most of U.S. history, the primary jack design has been the blue canton with stars (the "union") from the U.S. national ensign. The blue fielded, white-starred jack is referred to as the Union Jack, not to be confused with the Union Jack of Britain, which has the same name but a different design. Like the U.S. 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 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 U.S. federal agencies such as the U.S. Coast Guard, the Military Sealift Command and the National Oceanic and Atmospheric Administration Corps. The standard 50-star jack continues to be used by U.S. civilian ships and by U.S. yachts as well.