I’ve written about Thanksgiving history here many times (2005, 2006, 2008, 2010) and this year it feels like time to write again.
It is clear that the holiday was created by President Lincoln after Civil War to bring the pro-slavery rebels back to the table with their American neighbors and family.
Don’t know if I can do the topic any more justice, however, than a 2019 New Yorker article by a historian. So here is the TL;DR
Fretting over late-nineteenth- and early-twentieth-century immigration, American mythmakers discovered that the Pilgrims, and New England as a whole, were perfectly cast as national founders: white, Protestant, democratic, and blessed with an American character centered on family, work, individualism, freedom, and faith.
The new story aligned neatly with the defeat of American Indian resistance in the West and the rising tide of celebratory regret that the anthropologist Renato Rosaldo once called “imperialist nostalgia.” Glorifying the endurance of white Pilgrim founders diverted attention from the brutality of Jim Crow and racial violence, and downplayed the foundational role of African slavery. The fable also allowed its audience to avert its eyes from the marginalization of Asian and Latinx labor populations, the racialization of Southern European and Eastern European immigrants, and the rise of eugenics. At Thanksgiving, white New England cheerfully shoved the problematic South and West off to the side, and claimed America for itself.
Shocking reversal. Lincoln brought the pro-slavery forces back to the table and they pivoted on his gesture to a false cover-story while still enacting divisive racial violence.