Thanksgiving is observed in the United States every year on the fourth Thursday of November. This date was set by Congress on Dec. 26, 1941. The earliest possible date for Thanksgiving is Nov. 22, and the latest possible date is Nov. 28.
The first Thanksgiving feast in the United States took place in 1621, but it was not an annual holiday until 1863 when President Lincoln proclaimed the last Thursday in November as Thanksgiving. Succeeding presidents followed suit. In 1939, however, President Franklin Roosevelt broke with tradition and proclaimed the next-to-last Thursday of November to be Thanksgiving to provide a longer Christmas shopping season. Twenty-three states went along with the proclamation, but 23 others observed the traditional day. Texas and Colorado observed both days. The next year brought about similar confusion. Congress settled the issue with a law passed in 1941.
The holiday is based off of what Americans call the "First Thanksgiving" when the pilgrims celebrated their first harvest in the new world in 1621 alongside Native Americans. Americans continue that tradition by feasting alongside friends and family and giving thanks for what the year has brought them.