The Continental Union Flag first appeared on December 3, 1775.
The flag was raised aboard the Continental Navy flagship USS Alfred on the western shore of the Delaware River at Philadelphia. It combined the British Union Flag in the canton with thirteen alternating red-and-white stripes representing the United Colonies.
During the Revolutionary War, the design served as the flag of the United Colonies and functioned as the de facto national flag before Congress adopted the thirteen-star flag in 1777. Its British canton reflected the complicated political position of the colonies early in the war, when many colonists still hoped for reconciliation even as armed conflict continued.
The names Grand Union Flag and Cambridge Flag became common much later. During the Revolution, the design was also known as the Continental Colours or the flag of the United Colonies. It should not be confused with the Betsy Ross flag, a later thirteen-star design.