Happy Thanksgiving!

Thanksgiving or Thanksgiving Day also know as Turkey Day, celebrated on the fourth Thursday in November, has been an annual tradition in the United States since 1863, when during the Civil War, President Abraham Lincoln proclaimed a national day of thanksgiving to be celebrated on Thursday, November 26.

The event that Americans commonly call the "First Thanksgiving" was celebrated to give thanks to God for helping the Pilgrims of Plymouth Colony survive their first brutal winter in New England.The first Thanksgiving feast lasted three days, providing enough food for 53 pilgrims and 90 Native Americans.
The feast consisted of fish (cod, eels, and bass) and shellfish (clams, lobster, and mussels), wild fowl (ducks, geese, swans, and turkey), venison, berries and fruit, vegetables (peas, pumpkin, beetroot and possibly, wild or cultivated onion), harvest grains (barley and wheat), and the Three Sisters: beans, dried Indian maize or corn, and squash.The New England colonists were accustomed to regularly celebrating "Thanksgivings"—days of prayer thanking God for blessings such as military victory or the end of a drought. 

Traditional Celebration

In the United States, certain kinds of food are traditionally served at Thanksgiving meals. Firstly, baked or roasted turkey is usually the featured item on any Thanksgiving feast table (so much so that Thanksgiving is sometimes referred to as "Turkey Day"). Stuffing, mashed potatoes with gravy, sweet potatoes, cranberry sauce, sweet corn, other fall vegetables, and pumpkin pie are commonly associated with Thanksgiving dinner. All of these are actually native to the Americas or were introduced as a new food source to the Europeans when they arrived. Turkey may be an exception. In his book "Mayflower," Nathaniel Philbrick suggest that the Pilgrims might already have been familiar with turkey in England, even though the bird is native to the Americas. The Spaniards had brought domesticated turkeys back from Central America in the early 1600s, and the birds soon became popular fare all over Europe, including England, where turkey became a "fixture at English Christmases."

Source Wikipedia