It is perhaps little known that the first American flag displayed "at sea" was raised by Col. Wynkoop, commander of the Royal Savage, one of Benedict Arnold's little fleet in Lake Champlain, in 1776. This flag was a replica of the first striped flag, hoisted over Washington's headquarters at Cambridge. It consisted of thirteen alternate red and white stripes in the field and retained the colors of England, the united crosses of St. George and St. Andrew on a blue ground, in the canton. This flag was known in England as "The Rebellious Stripes."
    "A picturesque incident is told of the first Stars and Stripes used in a military engagement," said Mr. Ames, foremost flag manufacturer in the country. "The revolutionary flag of thirteen stripes with a circle of thirteen stars was adopted by the Continental Congress on June 14, 1777, but the statute was not officially promulgated until the 3d of the following September. Meanwhile a copy of an Albany newspaper describing the flag had fallen under the eye of a Continental officer from Massachusetts on his way with reinforcements to Fort Schuyler, formerly Fort Stanwix, where the city of Rome, N. Y., now stands.
    "He arrived at 5 p. m. on August 2 and very opportunely, too, as it turned out. For the British attacked the fort the following morning, which was Sunday. Before the end of the day the garrison had run up the first American battle flag. White stripes from shirts and hospital bandages alternated with red stripes made from the scarlet petticoat of a soldier's wife. A blue canton was improvised from the military coat of one Capt. Abraham Swartout, who, a year later, wrote to the commandant of the fort requesting 'an order on the commissary to supply me, as promised, with eight yards of broadcloth in lieu of my blue coat which was used for colors at Fort Schuyler.'"--From Everybody's Magazine for July.

Source:

Unknown, "First American Battle Flag," The Washington Post, Washington, D.C., Sunday, 25 July 1926, p. SM4.

    The "Col. Wynkoop" mentioned in the article above is Commodore Jacobus Wynkoop, whose story may be read here.

    All my best,

    Chris