Cooke's Wagon Road was the first wagon road between the Rio Grande and the Colorado River to San Diego, through the Mexican provinces of Nuevo México, Chihuahua, Sonora and Alta California, established by Philip St. George Cooke and the Mormon Battalion, from October 19, 1846 to January 29, 1847 during the Mexican American War. It became the first of the wagon routes between New Mexico and California that with subsequent modifications before and during the California Gold Rush eventually became known as the Southern Emigrant Trail.