There is a large oil refinery in Richmond, California, just a bit north/west of Oakland. It must be one of the oldest continuously operating such plants in the US. Built in 1901 by old Standard Oil, it made the land around it less desirable and therefore lower in price.
Blacks from the South came in large numbers to work in the shipyards during WWII. Housing was cheap and near work. They bought most of the houses offered.