On what date did Congress adopt the first national flag law of the United States?

Congress adopted the first national flag law of the United States on June 14, 1777.

The resolution stated that the flag would have thirteen alternating red and white stripes and thirteen white stars on a blue field, representing a new constellation. It did not specify the precise arrangement of the stars, leaving room for different designs. The resolution was adopted by the Second Continental Congress during the Revolutionary War.

The thirteen stripes represented the original thirteen states, which had begun as colonies. The stars represented the states in the Union and later increased as new states joined. In 1795, Congress changed the flag to fifteen stars and fifteen stripes after Vermont and Kentucky entered the Union.

The stripe count returned to thirteen in 1818, while the number of stars continued to change. The modern flag has fifty stars for the fifty states. Flag Day, observed on June 14, commemorates the 1777 resolution, although it was not made a federal holiday.