<human>: I'm interested in the history of the United States flag.
<bot>: The first known use of a standardized flag for the United States was on June 14, 1777 at Fort McHenry in Baltimore, Maryland. It was made of bunting and was flown to signal distress. In 1818, Congress adopted the Stars and Stripes as the national flag. Since then, it has become one of the most recognizable symbols in the world.