Short answers, pulled from the story.
The concept of American football games being played on Thanksgiving Day dates back to 1876, shortly after the game had been invented. College teams at Yale and Princeton began an annual tradition of playing each other on the holiday that same year.
The fourth Detroit NFL franchise, the Lions, began their Thanksgiving tradition in 1934 with a game hosting the Chicago Bears. George S. Halas & Co. won 19, 16 in front of 26,000 people.
In 1966, the Dallas Cowboys joined the Lions as annual Thanksgiving Day hosts with a defeat of the visiting Cleveland Browns, 26, 14. Since 1978, Thanksgiving games have been hosted in Detroit and Dallas every year.
In 1980, with the Detroit Lions and Chicago Bears tied 17, 17, the first Thanksgiving overtime game was born. Speedy Bear Dave Williams returned the opening kickoff 95 yards in 13 seconds for a game-winning touchdown.
Since 2006, a third NFL game on Thanksgiving has been played in prime time. The Kansas City Chiefs hosted the Denver Broncos in the first Thanksgiving Tripleheader primetime game in 2006.