First Navy Jack

The First Navy Jack is the current U.S. jack authorized by the United States Navy and is flown from the jackstaff of commissioned vessels of the U.S. Navy while moored pierside or at anchor. The design is traditionally regarded as that of the first U.S. naval jack flown in the earliest years of the republic.

In late 1775, as the first ships of the Continental Navy readied in the Delaware River, Commodore Esek Hopkins issued, in a set of fleet signals, an instruction directing his vessels to fly a "striped" jack and ensign. The exact design of these flags is unknown. The ensign was likely to have been the Grand Union Flag, and the jack a simplified version of the ensign: a field of 13 horizontal red and white stripes. It is likely that the colonial ships did not use (and could not have legitimately used) the canton of the Grand Union Flag (i.e., the Union Jack) as their jack given its use as a jack by Royal Navy warships. Despite the probability that the original jack may have been a simple striped flag, 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 tradition dates at least back to 1880, when 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 inferred design never actually existed but "was a 19th-century mistake based on an erroneous 1776 engraving".

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

...
Wikipedia