State Route 78 (Arizona–New Mexico) State Route 78 (Arizona–New Mexico) Arizona State Route 78 (SR 78) and New Mexico State Road 78 (NM 78) are a pair of adjoining state highways located in eastern Arizona and western New Mexico linking U.S. Route 191 (US 191) and Arizona State Route 75 near Greenlee County Airport to US 180 northwest of Cliff, New Mexico. It is also known in its Arizona stretch as Mule Creek Road. The western terminus of SR 78 is located at a junction with US 191 and SR 75 at Three Way, Arizona near Greenlee County Airport. The highway heads northeast from this
Interstate 10 in Arizona were laid out along railroad tracks, and US 60/US 70 was routed mostly parallel to the Santa Fe rail tracks east of Wickenburg, and the Arizona and California Railway west to Vicksburg. The two old federal routes then struck west across the desert and state line, picking up the Southern Pacific mainline at Indio, California, and I-10 overlies the old roads most of that distance. Moving east from the California line at Ehrenburg, I-10 follows the old route of US 60/US 70 for the first east from Blythe, California. In 1960, this western-most stretch of I-10 was built from near