The Pilgrims set ground at Plymouth Rock on December 11, 1620. The harvest of 1621 was a plentiful one. And the colonists decided to celebrate with a feast - including 91 Native Americans who had helped the Pilgrims survive their first year. The feast was more of a traditional English harvest festival than a true "thanksgiving" observance. It lasted three days. This is where the tradition of Turkey began, four men went out to hunt for a wild turkey for their Thanksgiving feast, this is also why Turkey is one of the main staples of Thanksgiving dinner today. 

The "Thanksgiving Feast" was not repeated tby the Pilgrims and Natives the year after that, as a matter of fact the day of Thanksgiving changed for over 100 years after the original first feast . Thanksgiving day was proclaimed a National Holiday in 1893 when President Lincoln  stated that Thanksgiving was going to be celebrated each year on the fourth Thursday in Novemeber. Thanksgiving has changed over the years, and has turned into the modern Thanksgiving Celebrations that are held today.