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
Arizona State Route 387 I-10. After the interchange with I-10, the highway intersects SR 187, with SR 387 turning towards the east at the intersection. The highway continues to the east-northeast until it reaches its northern terminus at SR 87. The route was established between 1946 and 1951, from SR 187 to SR 87 just south of Sun Lakes. Between 1958 and 1961, it was cancelled, and became part of SR 93, a proposed extension of US 93. In 1967, SR 387 was designated from SR 93 to SR 87. It extended south over part of SR 93 on December 17, 1984. Arizona State