While we would like to imagine that historically speaking, the church in America spoke out against slavery, what actually transpired occured more along the lines of geography, rather than theology:
With a few notable exceptions, each denomination made its own accommodation in due time, and the schism of the northern and southern branches merely strengthened a fait accompli.
Thus, the General Assembly of the Presbyterian Church declared in 1861 that the slave system had generally proven “kindly and benevolent” and had provided “real effective discipline” to a people who could not be elevated in any other way. Slavery, it concluded, was the black man’s “normal condition.”