The Second Continental Congress adopted the Flag Resolution defining the first U.S. flag on June 14, 1777.
The resolution specified thirteen alternating red and white stripes and thirteen white stars on a blue field. It stated that the stars represented a new constellation, linking the design to the thirteen states united in the new nation.
The resolution did not prescribe the star arrangement that Americans commonly recognize today. Early flags used several patterns, including circles, rows, and other arrangements. The number of stripes also changed temporarily to fifteen after Vermont and Kentucky joined the Union in the 1790s.
Congress restored the number of stripes to thirteen in 1818, while continuing to add stars as new states entered. The current fifty-star design dates from 1960, after Hawaii became the fiftieth state. June 14 is now observed annually as Flag Day in the United States.