In the mid-20th century, Upton's population swelled due to the popularity of the neighborhood and the pressures of state racial segregation that kept African Americans confined to certain areas in the city. Single family homes were subdivided into small apartments, and Pennsylvania Avenue's sidewalks were crowded on Saturday nights. Loud music and heavy drinking became popular vices of the newer Upton residents. Upper-income black families began abandoning the area for neighborhoods away from the center of the city, as part of the suburbanization under way in many cities.