The border between the San Pablo and El Sobrante Ranchos runs along the ridge separating the valleys through which Appian Way and May Road run. Both grants were made by the Mexican Government to members of the Castro family in 1834 and 1841, respectively. San Pablo Rancho lies on one side of the line and El Sobrante Rancho on the other, and much of what is thought of as El Sobrante, including the entire downtown, lies within the boundaries of the San Pablo Rancho.