Although it was adopted on June 14, 1777, when the Continental Congress resolved that the flag of the United States should "be 13 stripes alternate red and white, that the Union be 13 stars white in a blue field representing a new constellation," the origin of the national flag is somewhat obscure. Legend has it that George Washington asked Betsy Ross to produce the first American flag, but this story has never been proven true. Ross is known to have supplied flags to the Continental Navy. Before the Stars and Stripes, the nation's flag was the Continental Colors, which consisted of thirteen horizontal red and white stripes for the thirteen colonies and the British Union Jack as a symbol of the rebels' desire for the historic rights of British citizens. It is not known why the revolutionaries decided to replace the Union Jack with white stars.

Before that change, stars were uncommon on flags; since then, they have become popular. After Kentucky and Vermont joined the Union, two stars and two stripes were added to the flag. In this form, the flag inspired Francis Scott Key to write The Star-Spangled Banner. The design of the flag was changed again in 1818, retaining the thirteen stripes and adding stars to indicate the number of states in the Union at the time.

To date, the United States flag has been through twenty-seven versions, the most recent introduced on July 4, 1960, when Hawaii was admitted to the Union. Flags of the nineteenth century varied greatly in their star patterns, in the number of points on the stars, in the shades of red and blue, in the length-to -width ratio of the flag, and in other details. Until 1912, no official pattern existed for the arrangement of the stars. During the twentieth century, however, the design factors of the flag have been standardized.