In early 1775 the British siege of Boston had begun with April19th Battles of Lexington and Concord and the June 19th Battle of Bunker Hill. In June 1775 George Washington was made Commander in Chief of the Continental Army in Philadelphia. Washington set out immediately for Boston.
This flag was raised by the American militia under the command of George Washington on January 1st 1776 in Sommerville, Massachusetts, to celebrate the official formation of the American Continental Army. The flag was designed by simply adding six white rebellious stripes to the British red ensign creating 13 red and white stripes representing the 13 colonies. By keeping the British Union Jack in the flag the colonists showed they were not yet looking for total independence from England. This is sometimes known as the Cambridge or Grand Union Flag.
March 1776 the British commander William Howe saw the British position as indefensible and withdrew the British forces from Boston on March 17th 1776 to Halifax Nova Scotia.