It’s a warm summer evening and Devan Clapp is standing outside his two-story brick row house in northeast Baltimore’s Ramblewood neighborhood. The streets are quiet, with postage-stamp lawns; a transition area between the city and the suburbs of Baltimore County just a couple miles north. This neighborhood, like every other Baltimore neighborhood Clapp’s family has lived in the last hundred years, was predominantly white, before it wasn’t. He talks of how, in the 1980s, the skin color of his mother and father, godmother and brother, drove their white neighbors up and over to the “more-welcoming” side of the county line....