Hagerman Pass is a high mountain pass that crosses the Continental Divide in the Rocky Mountains of central Colorado. It passes the Sawatch Range, west of Leadville and connects the headwaters of the Arkansas river on the east end of the upper valley of the Fryingpan River above Basalt, in the basin of the Colorado River.

The pass is an unimproved state road that crosses streams and rocky sections at an apex of 11,925 feet, which is only passible by four-wheel-drive vehicles, bicycles, foot or by OHV’s such as ATV’s or side-by-sides. It is open approximately late May through the arrival of the first heavy snow in mid-to-late autumn and is occasionally blocked by fallen trees. During the rainy season, the road may be impassible due to standing water and excessive mud. Towards the top of the pass, the road becomes narrower with rock ledges dropping thousands of feet to the valley floors below. With the official pass being at 11,925 feet, the road reaches a slightly higher elevation south-southeast of the pass at 12,050 feet, another 75 feet higher than the pass itself.

The pass was named for James J Hagerman, builder of the Colorado Midland Railroad. The Colorado Midland Railroad crossed the Continental Divide through one of two tunnels—initially the Hagerman Tunnel in 1877 and later the Busk-Ivanhoe Tunnel in 1893—near the top of Hagerman Pass. The tunnels are now abandoned by the defunct CMR Railroad. The Hagerman Tunnel is 2,161 feet long and is at an elevation of 11,528 feet. There was a 1,084-foot long trestle built on the eastern approach of the tunnel that no longer exists. At the time of its construction, it was the highest tunnel ever built. The lower Busk-Iavanhoe Tunnel, is 9,394 feet long and sits at a lower elevation of 10,953 feet. It now serves as a water diversion tunnel, draining Ivanhoe Lake on the west side of the pass into the Arkansas River Basin. In 1922, it was covered with auto traffic as it was renamed the Carlton Tunnel and became part of Colorado State Highway 104. In 1942, the state discontinued maintenance of the road and the tunnel collapsed partially. Then in 1971, the tunnel was purchased by the Highline Canal company and was repaired at a cost of $50,000. Subsequently, the Board of Water Works in Pueblo, Colorado, bought half of the water rights and, in 1988, the City of Aurora bought the remaining rights.

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