The first Thanksgiving was celebrated in 1621, and President Lincoln proclaimed Thanksgiving a national holiday on 10/3/1863. 96% of Americans celebrate Thanksgiving, and along the way we spend $550 million buying turkeys. The first Thanksgiving college football game took place in 1876; the first NFL game in 1920. My secret to not gaining weight; eat slowly, go easy on the appetizers, drink lots of water, and wear tight-fitting clothes.