Final answer:
The first Thanksgiving celebration most likely occurred in September or October of 1621, as Pilgrims and Native Americans shared a harvest feast.
Step-by-step explanation:
The first Thanksgiving celebration likely took place in September or October of 1621. During this event, the Pilgrims, joined by Massasoit and about one hundred Indians, shared a feast that included venison, fish, fowl, and beer. This was a moment of collaboration and a brief respite from the hardships faced by the Pilgrims in the New World. Notably, this occasion was devoid of modern Thanksgiving staples such as pumpkin pie and cranberry sauce, and the participants ate largely with their hands.