One of the best-preserved early scenic drives for motorists, Skyline Drive was built for $6,400 by convict labor as a 2.5-mile excursion along the ridge of Cañon City's western hogback formation, with its precipitous dropoffs and fine views. Opened as a two-way buggy drive, it was later converted to a paved, one-way auto road with deep dips and steep hills. The arch (1932) at the west entrance contains rocks from every U.S. state and was also built by convict labor.