Thanksgiving is a national holiday in the United States. It is celebrated on the fourth Thursday of November. Thanksgiving day commemorates the first harvest and giving thanks for a good harvest.
It was originally celebrated by the Pilgrims, who came to America in 1620 from England. The Pilgrims were persecuted in their homeland and they wanted to start a new life with their own religion in America. They set sail on Mayflower and arrived at Plymouth Rock, which became the first settlement of the Pilgrims, on December 21st, 1620.
The first celebration of Thanksgiving happened on October 3rd, 1621 when they had enough food to last them through winter and they gave thanks for that good fortune.