The flag of the United States consists of 13 alternating red and white stripes and a blue canton containing 50 white stars. Each of the white stars represents one of the states in the United States of America. The number of stars, therefore, has changed over time to reflect the growing number of states in the Union.
The first official national flag, formally approved in 1777, had 13 stars, reflecting the 13 states at the time. The number of stars increased to 15 in 1795; this reflected the two new states that had been admitted in previous years. The Flag Act of 1818 increased the number of stars to 20, which reflected the country’s 5 new states. The 1818 act is also the one that explicitly states that the number of stars on the flag should always match the number of states, and that any new star should be added on the July 4 following a state’s admission to the Union.
There have been 27 versions of the flag between 1777 and 1960, with 25 of those changes involving the stars only. The most recent change was on July 4, 1960, to reflect Hawaii’s admittance to the Union in the previous year, bringing the total number of stars to 50.