Thanksgiving may be a national holiday today, but originally it was a "Yankee" holiday. As New Englanders migrated to other areas of the country, they took the holiday with them, spreading it south and west.
President Abraham Lincoln declared Thanksgiving a national holiday in 1863 during the Civil War to promote national unity. Thanksgiving had already spread, but white Southerners still tended to see it as a Yankee holiday, especially after Lincoln's proclamation.
So, after the Civil War, many white Southerners celebrated Thanksgiving on their own schedule or forwent the holiday altogether. Meanwhile, African Americans in the South embraced Thanksgiving, celebrating it along with the rest of the nation.
African-American pastor, Alexander Crummell, used the occasion of Thanksgiving in 1875 to deliver a powerful sermon, "The Social Principle Among a People and Its Bearing on Their Progress and Development." Crummell argued that it was the duty of himself and his congregation to reflect on racial progress on Thanksgiving Day, urging that "[i]t is peculiarly a duty at this time when there is evidently an ebb-tide of indifference in the country, with regard to our race; and when the anxiety for union neutralizes the interest in the black man. . . ."
It was not until the opening decade of the 20th century that white Southerners fully adopted the holiday as well. By the time President Franklin Roosevelt signed a bill permanently placing Thanksgiving on the fourth Thursday of November, it had been incorporated as a holiday celebrating family into the lives of most Americans.