Final answer:
The first NFL game played on Thanksgiving was in 1934, which started a long-standing tradition of Thanksgiving NFL games.
Step-by-step explanation:
The historic event often recognized as the first Thanksgiving NFL game took place in 1920. However, the information provided references the ceremonial first Thanksgiving feast in Plymouth in 1621, which was a gathering to celebrate the first harvest in the New World. This feast has historical significance as the origin of the modern Thanksgiving holiday. Over time, Thanksgiving has become associated with many traditions, including football games. The first Thanksgiving Day football game was actually played by the National Football League in 1934, with the Detroit Lions facing the Chicago Bears. This game started a tradition that continues to this day, with NFL games being a staple of Thanksgiving celebrations in many American households.