Why do the Detroit Lions and Dallas Cowboys always play on Thanksgiving?

For as long as most of us can remember, the Dallas Cowboys and Detroit Lions have played games on Thanksgiving Day. But why?

Let’s start with the Lions. They have played every Thanksgiving since 1934, with the exception of 1939-44, despite the fact they haven’t been a good team most of those years. The Lions played their first season in Detroit in 1934 (before that, they were the Portsmouth Spartans). They struggled their first year in Detroit, as most sports fans there loved baseball’s Detroit Tigers and didn’t come out in droves to watch the Lions. So Lions owner George A. Richards had an idea: Why not play on Thanksgiving?

Richards also owned radio station WJR, which was one of the biggest stations in the country at that time. Richards had a lot of clout in the broadcasting world, and convinced NBC to show the game nationwide. The NFL champion Chicago Bears came to town, and the Lions sold out the 26,000-seat University of Detroit field for the first time. Richards kept the tradition going the next two years, and the NFL kept scheduling them on Thanksgiving when they resumed playing on that date after World War II ended. Richards sold the team in 1940 and died in 1951, but the tradition he started continues today when the Lions play the Green Bay Packers.

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The Cowboys first played on Thanksgiving in 1966. They came into the league in 1960 and, as hard as it is to believe now, struggled to draw fans because they were pretty bad those first few years. General manager Tex Schramm basically begged the NFL to schedule them for a Thanksgiving game in 1966, thinking it might get them a popularity boost in Dallas and also nationwide since the game would be televised.

It worked. A Dallas-record 80,259 tickets were sold as the Cowboys defeated the Cleveland Browns, 26-14. Some Cowboys fans point to that game as the beginning of Dallas becoming “America’s team.” They have only missed playing on Thanksgiving in 1975 and 1977, when NFL Commissioner Pete Rozelle opted for the St. Louis Cardinals instead.

The games with the Cardinals proved to be losers in the ratings, so Rozelle asked the Cowboys if they would play again in 1978.

“It was a dud in St. Louis,” Schramm told the Chicago Tribune in 1998. “Pete asked if we’d take it back. I said only if we get it permanently. It’s something you have to build as a tradition. He said, ‘It’s yours forever.’ ”

Dallas takes on the Kansas City Chiefs on Thursday.

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This story originally appeared in Los Angeles Times.