Rancho San Luis Gonzaga was a 48,821-acre (197.57 km2) Mexican land grant in the Diablo Range, in present-day Santa Clara County and Merced County, California given in 1843 by Governor Manuel Micheltorena to Juan Carlos Pacheco and José Maria Mejía.[1] The grant was bounded by Francisco Pérez Pachecos Rancho Ausaymas y San Felipe on the west (at the top of present-day Pacheco Pass), the San Joaquin River and San Joaquin Valley on the east, and Los Baños Creek on the south.[2]