In 1843 the lake was incorporated in a land grant which formed Rancho Castac. In 1854, Fort Tejon was founded in the Grapevine Valley about northwest of the lake, to command the main route (via Tejon Pass) between the Central Valley and Southern California. The Rancho Castac was eventually acquired by Edward Fitzgerald Beale, who founded Tejon Ranch (at one point the largest private landholding in California).