Nautical Flags

David Aker
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There are three primary types of nautical flags:  jacks, yacht ensigns and signal flags.

The Jack

The jack of the United States of America is a maritime flag flown on the “jack staff” in the bow of American vessels that are moored or anchored. The U.S. Navy is a prime user of jacks but they are also used by ships of the U.S. Coast Guard and other U.S. government ships.  Civilian vessels are not precluded from using a jack.

The standard U.S. jack is a flag of 50 white stars on a blue field.  (Essentially, the canton of the United States Flag.)  It is used by the U.S. Coast Guard, the Military Sealift Command, NOAA, and other federal vessels as well as U.S. civilian ships and yachts.

The blue field, white-starred jack is referred to as the Union Jack, not to be confused with the British Union Jack.

Rules for flying the jack are similar to the American flag, except that the jack is only flown at the bow when the ship is anchored.

Since September 11, 2002, the U.S. Navy has flown the First Navy Jack (rather than the Union Jack).  The First Navy Jack is a flag bearing 13 red and white stripes, a rattlesnake and the motto “DONT TREAD ON ME” [sic].  The Secretary of the Navy directed the use of the rattlesnake jack in place of the union jack for the duration of the Global War on Terrorism.

The First Navy Jack:  A Brief History

The United States Navy, originated as the Continental Navy, was established by the Continental Congress on October 13, 1775.

By the War of Independence, the rattlesnake used in conjunction with the motto “Dont Tread on Me,” [sic] was a common symbol for the United States, its independent spirit, and its resistance to tyranny.

There is a widespread belief that ships of the Continental Navy flew a jack consisting of alternating red and white stripes, having the image of a rattlesnake stretched out across it, with the motto “Dont Tread on Me” [sic]. That belief, however, rests on no firm base of historical evidence.  The historical evidence makes it impossible to say for certain whether the Continental Navy used the striped rattlesnake flag as its jack. At the same time, the evidence does suggest strong connections between the symbol of the rattlesnake with the motto “Don’t Tread on Me” and the United States’ earliest naval traditions.

The Yacht Ensign

“The routine of life on board a yacht would be lost, confused, or rendered irksome, without the potent sway of the colors.  All the vital events of the day are ordered or indicated by the signals, and as they give tone and vigor to the inmate or inherent impulse to “Follow the Flag”, all sailors at least yield ready compliance.”   (Etiquette of Yacht Colors, Annin & Co., 1902)

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.

A special flag looking like the national flag but with a “fouled anchor” within a circle of white stars on a blue field for the canton.  This flag was created by Act of Congress in August 1848 as a flag to be used by licensed U.S. yachts.

This flag was originally used to declare vessels exempt from customs duties.  While formally licensed yachts were required to fly this ensign, unlicensed American yachts also started flying this flag as the ensign.  Eventually, the U.S. Navy recognized this practice for all American yachts. However, the national flag is the only ensign allowable for an American in international or foreign waters.

The yacht ensign is still widely flown by U.S. yachts and pleasure boats in U.S. waters today, continuing a tradition that dates back to 1848.  The United States Power Squadrons’ guide to flags and flag etiquette, prepared in consultation with the Coast Guard, Coast Guard Auxiliary, New York Yacht Club, and others, provides that the Yacht Ensign may be flown on recreational boats of all types and sizes instead of the national ensign in domestic waters.

Signal Flags

There are various methods by which the flags can be used as signals:

  • each flag may indicate a specific letter or number, or
  • individual flags may have a specific and standard meanings, and/or
  • one or more flags may form a code word.


  1. Department of the Navy — Naval History and Heritage Command
  2. Raven, A Journal of Vexillology, North American Vexillological Association, Volume 11 – 2004
  5. Etiquette of Yacht Colors, Annin & Co., 1902
  6. Wikipedia