In August 1863, Archbishop Joseph Sadoc Alemany, OP, opened St. Mary's College at this location with a faculty of two diocesan priests, four laymen, and two student teachers. In August 1868, at the invitation of the archbishop, Brother Justin McMahon and seven Christian Brothers took charge of St. Mary's. The Christian brothers have manifested principles characterized by the best educational institutions: excellence.

California Registered Historic Landmark No. 772

Plaque placed by the California State Parks Commission in cooperation with St. Mary's College, its alumni and the California Historical Society, September 29, 1962.