The 13 stripes on the American flag represent the original 13 colonies, and the 50 stars represent the number of states in the Union. Originally, both were meant to represent American states, but since 1818, the number of stripes has been standardized at 13.
The initial design of the United States flag included one stripe and one star for each state in the Union. There were 13 states in 1776. In 1795, the admission of Vermont and Kentucky required an updated design, and for a time, the American flag bore 15 stars and 15 stripes. Francis Scott Key wrote about this version of the flag in "The Defence of Fort M'Henry," which later became "The Star Spangled Banner" and America's national anthem.
By 1818, the admission of Tennessee, Ohio, Louisiana, Indiana and Mississippi made the addition of a stripe for each state unsustainable. A new law set the standard at 13 stripes, with the number of stars to be updated every 4th of July as new states entered the Union. Over the years, there have been 39 official United States flags.
In its current design, the American flag's 13 stripes are equal in size, and the colors alternate between red and white. The 50 white stars appear in a blue rectangle located in the flag's canton, or union.