The road is 74.3 miles (119.6 km) long and runs from U.S. Route 180 (US 180) west of Reserve to US 60 in Datil.

NM 12 is located entirely within Catron County.

The road's original alignment ran south from its western terminus to near Mule Creek, but this section was later removed.

The road was designated a State Highway by the New Mexico legislature in 1917.

Geographic data related to New Mexico State Road 12 at OpenStreetMap