The American tradition of Thanksgiving began with a three-day feast that took place in 1621 to celebrate a bountiful harvest. It became cemented as an annual celebration in 1863, when President Lincoln declared a "day of Thanksgiving" in the midst of the Civil War.
The Pilgrims started the Thanksgiving tradition because they were so happy to have survived their first brutal winter and to have made a successful harvest with the help of the Native Americans in the area. After the Pilgrims celebrated the first Thanksgiving in 1621, they celebrated with other feasts from time to time but not on an annual basis. Throughout colonial times, the holiday continued to be celebrated sporadically, without any coordination between the different colonies. During the Revolutionary period, the governing bodies of the new United States began to call for days of giving thanks, and in 1789 President George Washington proclaimed the first national day of "thanksgiving and prayer." The holiday did not become an annual tradition at that point, but different states and individuals continued to celebrate it. Finally, with Lincoln's proclamation, the holiday became an annual tradition at the national level. The holiday has undergone only one major change since then: in 1939. President Franklin Roosevelt changed its date from the final Thursday in November to the next-to-last Thursday in November. He made this change in hopes that a longer Christmas shopping season would boost retailers' profits.