Last month, at a day-long symposium sponsored by the museum, the rise of Chocolate City was contrasted with the city’s more recent gentrification. In 2011, the percentage of Black residents in Washington fell below 50 percent for the first time in over half a century. Howard Gillette, professor of history emeritus at Rutgers University, observed that in many respects the District of Columbia has become “ground zero for gentrification and social justice issues that are going on nationally.”