On what date did Congress adopt the first U.S. national flag design?

Congress adopted the first U.S. national flag design on June 14, 1777.

The Second Continental Congress passed the First Flag Resolution, which specified thirteen alternating red and white stripes and thirteen white stars on a blue field. The resolution did not prescribe the exact arrangement of the stars, so early flags could differ in appearance.

June 14 is now observed in the United States as Flag Day. The first resolution came nearly a year after the Declaration of Independence and during the Revolutionary War, when the new nation needed a recognizable national symbol for military and diplomatic use.

A common mix-up is to assume that the original flag had fifty stars. The number of stars expanded as new states joined the Union, while the number of stripes was later fixed at thirteen to represent the original colonies. The modern flag’s familiar fifty-star design dates from 1960, after Hawaii became a state.