Most Americans acknowledge the first Thanksgiving as a meal shared by Pilgrims and Native Americans in 1621. However, the holiday was not official until declared so by Abraham Lincoln in 1863.
The former occasion occurred after the Pilgrims' first harvest in the New World. They feasted for three days, with fare including cooked wild turkeys. It was more than 240 years later, however, that Lincoln decreed the last Thursday in November to be a national day of thanksgiving to commemorate the Union's victories at Gettysburg and Vicksburg. Together, the two occasions form the basis of the American holiday celebrated by millions today.