After the Spanish founded Mission San Gabriel in 1771, the Chino Hills region was used extensively for grazing by mission cattle. During the Mexican Republic era, the hills were used as spillover grazing from such surrounding Mexican ranchos as Santa Ana del Chino and Rancho La Sierra (Yorba). After Mexico ceded California to the United States it was, and still is, a swamp and subject to flooding annually. Most historical dwellings were demolished in the rush to develop the modern city. A local state monument is present in the grass lawn area of the local fire department. Casa Colina, a well-known rehabilitation center now situated in Pomona California, began as a tubercular clinic in the Los Serranos sector.