The English colonists we call Pilgrims celebrated days of thanksgiving as part of their religion. But these were days of prayer, not days of feasting. Our national holiday really stems from the feast held in the autumn of 1621 by the Pilgrims and the Wampanoag to celebrate the colony's first successful harvest.
According to what traditionally is known as "The First Thanksgiving," the 1621 feast between the Pilgrims and the Wampanoag at Plymouth Colony contained waterfowl, venison, ham, lobster, clams, berries, fruit, pumpkin, and squash.
William Bradford and the First Thanksgiving. As was the custom in England, the Pilgrims celebrated their harvest with a festival. The 50 remaining colonists and roughly 90 Wampanoag tribesmen attended the "First Thanksgiving."
The holiday feast dates back to November 1621, when the newly arrived Pilgrims and the Wampanoag Indians gathered at Plymouth for an autumn harvest celebration, an event regarded as America's “first Thanksgiving.”