The Rockaway beach area has played a role in local history since the arrival of the Portola Expedition, the Spanish explorers credited with discovery of the San Francisco Bay. As early as 1776, limestone was quarried in the Rockaway Beach lime pits and was used to whitewash the newly built Presidio of San Francisco . More recent investigations suggest that early settlements in San Pedro Valley also used this limestone for their foundations. In 1907, the Rockaway Beach quarry was established as a continuously-operating commercial entity known as the Stone Brothers. After construction of the Ocean Shore Railroad in 1907, limestone from this quarry was conveyed to assist with the rebuilding of San Francisco after the 1906 San Francisco earthquake. Quarry materials were actually used as ballast for the trackbed of the railroad; moreover, after completion of the railroad, Rockaway Beach was considered a suburb of San Francisco due to convenient access. This all changed after legal problems resulting from landslide repair caused the railroad to go bankrupt in 1921.