On March 4, 1791, Vermont became the first state added to the union following the ratification of the U.S. Constitution. Kentucky joined the Union on June 1, 1792 and made the count fifteen.
On this day in history, President George Washington approved an act calling for the Flag of the United States to have fifteen stripes and fifteen stars, reflecting the admission of Vermont and Kentucky to the Union. (You can read The Flag Act of 1794 (1 Stat. 341) here.)
The new regulation signed by Washington went into effect on May 1, 1795.
By 1818, six additional states had joined the union – Tennessee, Ohio, Louisiana, Indiana, Mississippi and Illinois. The decision was made that year to return the number of stripes on the flag to 13 in recognition of the number of original colonies and increase the number of stars to equal the number of states. The Flag Act of April 4, 1818 (3 Stat. 415) (you can read the text here) established the modern rule of having thirteen stripes to represent the original thirteen colonies and having the number of stars match the number of states. It also provided that subsequent changes in the number of stars take effect on the fourth day of July succeeding a state’s admission.