According to the author, both Martin Luther King Jr and Coretta Scott King attended Unitaroan churches at times and considered becoming Unitarians, but decided not to, in part because of the near nonexistance of black Unitarian churches.
So, with a POD of 1900, what would it take to grow African American UU churches such that a young MLK (or some other young and charisnatic black man in the 50s) migyt become a UU minister?