The First Navy Jack was the naval jack of the United States from 1975 to 1976 and again from 2002 to 2019. It was authorized by the U.S. Navy and was flown from the jackstaff of commissioned vessels of the U.S. Navy while moored pierside or at anchor. Since then, it is used only as a naval jack by the oldest active warship in the U.S. Navy.^{[lower-alpha 1]} The design is traditionally regarded as that of the first U.S. naval jack, flown soon after independence, but this is not supported by the historical record.

The First Navy Jack was replaced as the U.S. naval jack by the U.S. Union Jack (consisting of white stars on a blue field, not to be confused with the flag of the United Kingdom, also commonly called "the Union Jack") on June 4, 2019, by order of the Chief of Naval Operations.^[1][2][3]

In late 1775, as the first ships of the Continental Navy readied in the Delaware River, Commodore Esek Hopkins issued an instruction directing his vessels to fly a "striped" jack and ensign. The exact design of these flags is unknown. But, since about 1880, this jack has traditionally been depicted as consisting of thirteen red and white stripes charged with an uncoiled rattlesnake and the motto "Dont Tread on Me" [sic]; this design appeared in a color plate in Admiral George Henry Preble's influential History of the Flag of the United States. Recent scholarship, however, has demonstrated that this design never existed but "was a 19th-century mistake based on an erroneous 1776 engraving".^[4]

In 1778, John Adams and Benjamin Franklin wrote a letter to the Ambassador of the Kingdom of Sicily, thanking him for allowing entry of revolutionary ships into Sicilian ports. The letter describes the new flag of the colonies according to the 1777 Flag Resolution, but also describes a flag of "South Carolina, a rattlesnake, in the middle of the thirteen stripes."^[5]

The rattlesnake had long been a symbol in the colonies of resistance and defiance to the Crown. The phrase "Don't Tread on Me" may have been coined during the American Revolutionary War, a variant perhaps of an earlier image. A snake severed in segments and labelled with the names of the colonies and the legend "Join, or Die", had first been published in Benjamin Franklin's Pennsylvania Gazette in 1754, as a political cartoon reflecting on the Albany Congress.

The rattlesnake (specifically, the Timber Rattlesnake) is especially significant and symbolic to the American Revolution. The rattle has thirteen layers, signifying the original Thirteen Colonies. Additionally, the snake does not strike until provoked, a characteristic expressed by the phrase "Don't tread on me" (see Gadsden flag).

Typically the flag's rattlesnake is depicted with red scales on its back,^[6] but some have depicted the snake as all-gold.^[7][8][9]

Like other snake flags, the First Navy Jack has been used by non-Navy people in protest or commemoration. For example, opponents to a smoking ban in Franklin, Indiana, flew Navy Jacks outside their homes and businesses.^[16] A First Navy Jack flag was also placed at a makeshift memorial on Boylston Street after the Boston Marathon bombing.^[17][18]

• Ensign of the United States
• Bibliography of early United States naval history