How did Thanksgiving become a holiday? In Autumn 1621, the Plymouth colonists and the Wampanoag Indians shared a three-day harvest feast, which was considered the first Thanksgiving. They feasted on deer, geese, oysters, corn, onions, pumpkins, squash, and dried fruits. This tradition continued every year, but was not an official ‘holiday’, simply a celebration and gathering. It wasn’t until 1863 that President Abraham Lincoln declared the last Thursday in November a national day of Thanksgiving. Then in 1939, President Roosevelt moved Thanksgiving up a week to create a longer Christmas shopping season hoping to spur retail sales during the Great Depression. There was such a public uproar about this decision that President Roosevelt had to move Thanksgiving back. In 1941, Congress sanctioned Thanksgiving a legal holiday on the fourth Thursday in November.
For more on the history of Thanksgiving, please visit http://www.history.com/topics/thanksgiving