The first American Thanksgiving was celebrated in 1621.The colonists celebrated it as a traditional English harvest feast, to which they invited the local Wampanoag Indians with out who's helped they would have starved.
George Washington was the first president to declare the holiday, in 1789.
In 1863 a Abraham Lincoln, searching for a way to unite the nation issued a proclamation declaring the last Thursday in November a day of thanksgiving.
Starting in 1939, Franklin D. Roosevelt, seeking to lengthen the Christmas shopping season, proclaimed Thanksgiving the third Thursday in November. Controversy followed, and Congress passed a joint resolution in 1941 decreeing that Thanksgiving should fall on the fourth Thursday of November, where it remains.
Be thankful for and enjoy your family and friends, they are what it's about.
Have a Happy Thanksgiving!