To start off, Thanksgiving is a national holiday that is  celebrated in Canada and the US. In fact thanksgiving was originally just a  day to celebrate giving thanks for the blessing of harvest.Here in the U.S thanksgiving day is celebrated the fourth Thursday of November. The 1st thanksgiving was celebrated by pilgrims in the new world in the year 1621. In September 1620 a ship left Plymouth, England, carrying 102 passengers.The pilgrims were seeking a new home in which they could practice their own beliefs. Although in march they received a visit from an Abenaki Indian which greeted them. Later on days pass and he turned with another native american. They taught the pilgrims how to catch food and ways to get other food.Therefor, in 1621 was when the first thanksgiving happened.After all this the  pilgrims celebrated their successful year in harvest. In 1623 the pilgrims held another thanksgiving dinner to mark the end of a long drought which threatened the year's harvest.