Note:

From Abraham Lincoln Online:

"Prior to this, each state scheduled its own Thanksgiving holiday at different times, mainly in New England and other Northern states. President Lincoln responded to Mrs. Hale's request immediately, unlike several of his predecessors, who ignored her petitions altogether. In her letter to Lincoln she mentioned that she had been advocating a national thanksgiving date for 15 years as the editor of Godey's Lady's Book. George Washington was the first president to proclaim a day of thanksgiving, issuing his request on October 3, 1789, exactly 74 years before Lincoln's."

Links:

Zimbardo's Heroic Imagination Project

The Mendota Study