Thanksgiving has its roots in English traditions of harvest festivals and religious observances. The Pilgrims, who were English settlers in Plymouth, Massachusetts, are often associated with the first Thanksgiving celebration in America. In 1621, after a successful harvest, they invited the Wampanoag Native Americans to join them in a three-day feast to give thanks for their blessings. However, this event was not considered a significant holiday at the time.

Thanksgiving as we know it today was established much later. In 1789, President George Washington proclaimed a national Thanksgiving day to be celebrated on November 26th. It was intended as a way for the new nation to express gratitude for the end of the Revolutionary War and the ratification of the Constitution.

In the mid-19th century, Sarah Josepha Hale, an influential writer and editor, campaigned for Thanksgiving to become a national holiday. She believed it would help unify the country during a time of division, particularly leading up to the Civil War. Abraham Lincoln finally heeded her request and, in 1863, proclaimed Thanksgiving as a national holiday to be celebrated on the last Thursday of November.

For many years, Thanksgiving remained on the last Thursday of November until 1939, when President Franklin D. Roosevelt moved it up a week to stimulate the economy during the Great Depression. This decision was met with mixed reactions and confused the public. Eventually, in 1941, Congress officially established Thanksgiving as the fourth Thursday of November, where it remains today.