Who established the Thanksgiving holiday and for what reason?

The establishment of Thanksgiving as a national holiday is attributed to Abraham Lincoln, who proclaimed the holiday in 1863 during the Civil War. His aim was to create a unified national observance of gratitude, rather than simply a harvest celebration. He designated the last Thursday of November as a day for "Thanksgiving and Praise to our beneficent Father who dwelleth in the Heavens."

Lincoln's motivation was to foster a sense of unity and reconciliation during a time of great national strife, recognizing the importance of gratitude in healing and bringing the country together. The other options do not accurately represent the historical context or significance behind the establishment of Thanksgiving. George Washington did issue a Thanksgiving proclamation, but it did not create the holiday in the way Lincoln's did. Franklin D. Roosevelt's involvement came later when he aimed to make Thanksgiving more commercial, and John Adams' contributions were not related to the establishment of Thanksgiving at all.

Thus, Lincoln’s proclamation stands as a crucial moment in American history, establishing a time for collective appreciation for the blessings of the past while looking forward to unity and hope for the future.