The second United States flag law added two stars and two stripes for Vermont and Kentucky. It was the country’s only official design period with more than thirteen stripes.
Specification boundaries
The act approved on 13 January 1794 required fifteen alternating stripes and fifteen stars from 1 May 1795. It did not prescribe the flag’s proportions, the union dimensions, or the arrangement and orientation of the stars.
The surviving banner
Mary Pickersgill made the best-known 15-star example for Fort McHenry in 1813. Its stars were arranged in five staggered rows of three, and its original dimensions were approximately 30 by 42 feet. That artifact inspired Francis Scott Key in September 1814.
Return to thirteen stripes
The flag act of 4 April 1818 restored thirteen stripes and established a star for every state, with new stars taking effect on the Fourth of July after admission. The change superseded the 15-stripe form on 4 July 1818.
Source trail
Smithsonian Institution: principal flag acts and star-count periods ↗
National Museum of American History: visual description of the Star-Spangled Banner ↗