The June 14, 1777 measure that established the first official U.S. flag is called the Flag Resolution.
The Second Continental Congress adopted the resolution during the Revolutionary War. It specified thirteen alternating red and white stripes and a union of thirteen white stars on a blue field. The stars and stripes represented the thirteen United States and a new constellation.
The resolution did not prescribe a particular arrangement for the stars. Early flags therefore used several patterns, including rows, circles, and other layouts. The familiar Betsy Ross pattern is one later traditional arrangement, but the resolution itself did not name Betsy Ross or require a circle of stars.
Congress later changed the flag as new states joined the Union. In 1795, both stars and stripes rose to fifteen; in 1818, the stripes returned to thirteen while new stars continued to be added. The present flag has fifty stars and thirteen stripes.