Rancho Arroyo de Las Nueces y Bolbones (also called "San Miguel") was a 17,782-acre (71.96 km2) Mexican land grant in present-day Contra Costa County, California given in 1834 by Governor José Figueroa to Juana Sanchez de Pacheco. The grant was named after the principal waterway, Arroyo de los Nueces (walnut creek) and for the local group of indigenous Americans (Bolbones). The grant was on the western slope of Mount Diablo and includes the present day Walnut Creek. Approximately a quarter of the original rancho is now in the Mt. Diablo State Park.