State Road 478 (NM 478) is a 24.342-mile-long (39.175 km) state highway located entirely within Doña Ana County, New Mexico. Starting in Anthony and ending in Las Cruces, NM 478 was once a section of historic US 80, a major transcontinental highway between San Diego, California and Savannah, Georgia. In 1946, it also became part of U.S. Route 85, when the latter highway was extended south to the Mexican border in El Paso, Texas. US 80 and US 85 were rerouted onto a newer alignment to the east in the mid 1950s. This was also around the time the older highway was designated NM 478. For two years, the southern terminus of NM 478 also served as the national western terminus of US 80 until that highway was removed from New Mexico completely in 1991. Today, NM 478 remains on much the same route it has since it was first designated and serves several old US 80/US 85 communities long since bypassed by I-10

U.S. Route 80 was a major transcontinental highway in the U.S. state of New Mexico from November 11, 1926, to October 12, 1991. Nationally, US 80 stretched from San Diego, California to Tybee Island, Georgia, going through southern New Mexico from El Paso, Texas, through the towns of Las Cruces, Deming and Lordsburg before entering Arizona. US 80 was a modest 191 miles (307 km) long and was eventually replaced by Interstate 10 leading to the complete removal of US 80 in New Mexico. State Road 80 is a remnant of this route.