The Front Range of the Rocky Mountains W. of Denver is bounded by a foothills monocline of steeply dipping sedimentary rocks. The sediments are cut by the Golden fault, a prominent strike fault which parallels the mountain front for a distance of about 10 mi. The Golden fault was interpreted originally as a high-angle reverse fault and later as a low-angle thrust. However, fault relationships at the surface are not conclusive for either interpretation, In 1955, exploration for oil resulted in drilling along the fault zone S. of the town of Golden. Two wells in the Soda Lakes area show that the primary mountain flank structure is a large anticlinal fold which has a faulted and overturned limb. The Golden fault, therefore, is a secondary feature of the mountain flank fold and is not a major structure. The subsurface data are known to many geologists working in the area, but the details have not been previously published. Furthermore, the structural interpretation is particularly applicable to the study of mountain flank structure in other Rocky Mountain areas.