Thanksgiving and where it comes from

The first day of thanksgiving took place in 1637 amidst the war against the Pequots.
700 men, women, and children of the Pequot tribe were gathered for their annual green corn dance on what is now Groton, Connecticut.
Dutch and English mercenaries surrounded the camp and proceeded to shoot, stab, butcher and burn alive all 700 people. The next day the Massachusetts Bay Colony held a feast in celebration and the governor declared "a day of thanksgiving." In the ensuing madness of the Indian extermination, natives were scalped, burned, mutilated and sold into slavery, and a feast was held in celebration every time a successful massacre took place.

The killing frenzy got so bad that even the Churches of Manhattan announced a day of "thanksgiving" to celebrate victory over the "heathen savages," and many celebrated by kicking the severed heads of Pequot people through the streets like soccer balls.