The county is named for the Stanislaus River, first discovered by Gabriel Moraga in 1806, and later renamed Rio Estanislao in honor of Estanislao, a mission-educated renegade Native American chief who led a band of Indians in a series of battles against Mexican troops until finally being defeated by General Mariano Vallejo in 1826. Estanislao was his baptismal name, the Spanish rendition of Stanislaus, itself the Latin rendition of the name of an 11th century Catholic saint from Poland, St. Stanislaw.