The current United States flag has 13 stripes, representing the original thirteen colonies.
The stripes alternate red and white across the flag. Their number remained thirteen even as the United States expanded from its original states to the present fifty. The blue canton contains stars representing the states, so the stars—not the stripes—change when new states join the Union.
The Continental Congress established the basic stars-and-stripes design in its Flag Resolution of June 14, 1777. That resolution specified thirteen alternating red and white stripes and thirteen white stars on a blue field. It did not prescribe a particular arrangement for the stars, allowing early flags to appear in circles, rows, or other patterns.
Congress temporarily increased the flag to fifteen stripes in 1795 after Vermont and Kentucky joined the Union. The Flag Act of 1818 restored the number to thirteen and established the practice of adding a star for each new state. The current design has 50 stars, added after Hawaii became a state in 1959.