From 1847, Mormons pioneered the wagon road that became the Mormon Road from Salt Lake City to Los Angeles closely following the route of the Old Spanish Trail from Parowan, Utah. They followed the Mojave River from the Fork of the Road to the Lower Narrows, and left the river for the Cajon Pass on the route Frémont had found. In 1849, Forty-niners late on the main trail to California used the Mormon Road as a winter alternative route to California, referring to it as the "Southern Route" of the California Trail. Later emigrants to California followed the same route during the winter months. In 1855, the Mormon Road was improved and the route changed in places, becoming a major commercial wagon route between Utah and southern California, ending Utah's winter isolation until the railroads arrived there in 1869.