Every school child used to learn that the event happened in Plymouth, Massachusetts in 1621. After surviving a harsh winter in the new world, a sturdy band of Pilgrims met with their Wampanoag neighbors to celebrate the harvest. It was assumed that they feasted on turkey, with some of the trimmings, and began a tradition that continues to the present day.
In recent decades that version has been challenged by historical research and competing claims about the origins of Thanksgiving.