Rockridge is named for the outcroppings of rock at the northern end of the long shutter ridge formed by the Hayward Fault which encloses the linear valley in which the Montclair district of Oakland is situated. An example of this rock can be seen at an abandoned quarry adjacent to the Rockridge Shopping Center on Pleasant Valley Road. This quarry was operated well into the 1950s and is now used as a reservoir for the Claremont Country Club. Prior to the construction of the shopping center in the late 1960s, the Broadway side of the shopping center had a used car lot.