Víctor Castro and his brother Juan José Castro were the grantees of Rancho El Sobrante in 1841. Víctor Castro was elected as a juez de campo (field judge) in 1840 which gave him authority over roundups and branding of cattle in the area. He was a renowned horseman and helped battle indigenous raiders who attacked other Mexican ranchos. He also warred with American immigrants who squatted on his land after the California Gold Rush. Castro was a local leader in times of both peace and conflict. He remained active as a community leader after the annexation of California and was elected a Contra Costa County supervisor in 1852.