For Lincoln, the Plains Indians were not only an obstacle to the construction of railroads, but also an obstacle to his dream of making America a white ethno-state, which is why he fought for decades to deport all blacks from the United States to black colonies, or, reservations of a sort, which were in outside lands.
To realize his racially pure utopia, Lincoln became a member and leader of the American Colonization Society, an organization created to publicly encourage and finance the removal of freed blacks in America to Africa, or the “back to Africa” movement as it’s widely recognized today.
