This geologic map database is a digitized version of the original 1:24,000-scale analog geologic map titled "Preliminary geologic map of the Monkeys Head quadrangle, Mohave and La Paz Counties, Arizona", published by the U.S. Geological Survey (USGS) in 1988. The Monkeys Head 7.5-minute quadrangle is located at the confluence of the Colorado and Bill Williams Rivers in westernmost Arizona. This area is in the Basin and Range Province, which is characterized by mountain ranges and intervening alluviated valleys. The Colorado Plateau lies 150 km to the east, separated from the Basin and Range in Arizona by the Transition Zone. The mountains in the northern and central parts of the Monkeys Head quadrangle are northwest-trending, southwestwardly tilted blocks of Proterozoic metaplutonic rocks and Tertiary volcanic and sedimentary strata. The tilt is indicated by the steep to gentle southwest dip of Tertiary strata and underlying Tertiary-Proterozoic nonconformity. The tilted rocks are buried in the southern span of the quadrangle by nearly flat-lying upper Miocene lava flows that fringe the Buckskin Mountains. The entire quadrangle lies in the upper plate of a regional detachment fault system exposed in the Whipple, Buckskin, and Rawhide Mountains.