The Wind River Canyon is in Fremont and Hot Springs counties, central Wyoming, and constitutes one of the many scenic areas of the Rocky Mountain region. The canyon was formed by the Wind River cutting through the Bridger-Owl Creek Range. It has a length of 15 miles and reaches a depth in places of half a mile. Exceptional opportunity is offered the geologist to study the stratigraphy and structure because of the great number of outcrops and the great relief. Rocks ranging from pre-Cambrian to Eocene in age are exposed in the canyon and its vicinity. The part that faulting plays in mountain building is exceptionally well shown, and much evidence bearing on the controversy, whether or not most of the ranges of the region are vertical uplifts or ramp structures, is obtainab e. The Bridger-Owl Creek Range is an east-west trending asymmetrical anticline which has undergone much faulting on the south flank. Both normal and reverse faults are present, and the fault at the south portal is low in angle. This thrust developed during uplifting after it became easier for the strata to move on a thrust plane rather than to be uplifted further. As the force was still being applied the axis rotated toward the horizontal until the crestal area became totally unsupported. It then broke free resulting in the large normal fault at Boysen Dam. Uneven settling of this block produced the wedges bounded by normal and reverse faults.