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 as new states have been admitted to the Union.
The first official national flag was formally approved in a resolution on June 14, 1777; regarding the stars, it mandated “the union be thirteen stars, white in a blue field representing a new constellation.” The exact layout of the stars was not specified, so flag makers used different patterns. One common design had the 13 stars arranged in a circle. Subsequent versions of the flag have had rows of stars. The number of stars increased to 15 with the Flag Act of 1794, implemented in 1795; this reflected the two new states that had been admitted since 1777. The Flag Act of 1818 again raised the number of stars, to 20, to reflect 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. The last time a star was added to the flag was in 1960, to reflect Hawaii’s admittance to the Union the previous year.