On what date did Congress adopt the 13-star United States flag design?

Congress adopted the 13-star United States flag design on June 14, 1777.

The Continental Congress’s Flag Resolution specified 13 alternating red and white stripes and 13 white stars on a blue field. The stars represented the new union of the 13 states, while the stripes preserved a visual connection to the colonies that had declared independence.

June 14 is now observed as Flag Day in the United States. The resolution did not prescribe a single arrangement for the stars, so early flags used circles, rows, and other patterns. The familiar circular arrangement is often called the Betsy Ross pattern, but historians have not established that Ross designed the national flag.

The flag later changed as states joined the Union. Congress briefly increased both stars and stripes to 15 in 1795, but an 1818 law restored 13 stripes and established the practice of adding a star for each new state.