[5] The exact historical appearance of this flag is disputed, but it is displayed today by the Navy bearing a rattlesnake and motto.

The oldest commissioned warship in active U.S. naval status (that is, having the longest total period in active status) that is not the USS Constitution (technically the oldest commissioned ship in the U.S. Navy but is only used for ceremonial purposes) or the USS Pueblo (captured by North Korea in 1968 and is still commissioned in the U.S. Navy; it is currently a museum ship) flies the First Navy Jack, and is the only active U.S. warship that flies a different jack than the Union Jack.

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.

[7] The 48 star version of the Union Jack flag became official in 1912 after Arizona and New Mexico became states.

However, the standard U.S. jack (i.e. 50 white stars alternative in columns of four and five defacing a blue field) continued 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 and by U.S. civilian ships and by U.S. yachts.

[12][a] On February 21, 2019, the Chief of Naval Operations directed that U.S. Navy warships fly the U.S. jack again beginning on June 4, 2019.

[13][14] The oldest active U.S. warship flies the First Navy Jack; that ship has been USS Blue Ridge since 2014.

MSC and non-U.S. Navy vessels, such as those of the U.S. Coast Guard and NOAA, continued to use the 50-star union jack that was adopted in 1960.