Answer:
Thanksgiving is a national occasion in the United States, celebrated on the fourth Thursday of November. It started as a collect celebration. The occasion that Americans generally call the "Main Thanksgiving" was commended by the Pilgrims after their first reap in the New World in October 1621.
The National Thanksgiving Proclamation was the main formal declaration of Thanksgiving in the United States. President George Washington announced Thursday, November 26, 1789 as multi day of open thanksgiving and petition.