Climax Mine Main Entrance, Colorado

The Climax Mine was the largest molybdenum mine in the world, and was the origin of the company that is now called Climax Molybdenum. Climax Molybdenum operates this site as well as the Henderson underground mine, which has replaced this as the largest molybdenum mine in the nation, in output. The mine at Climax is bigger in surface area, and is directly on the Continental Divide. The main mine entrance is on Highway 91, at Fremont Pass, named after the explorer John Fremont. Climax got its name from railroad engineers who built a line to the top of the pass—the climax—in the late 1880s, connecting it to the boomtown of Leadville in the valley below. The mine operated mostly as an underground operation, starting in 1915. By 1926, three fourths of all the molybdenum in the world came from here. Block-cave mining started in 1927, an excavation technique that was pioneered at the mine. The process uses explosives to cause controlled cave-ins in massive vertical cavernous voids. Under its own weight, the broken material spills into pre-constructed funnels and is hauled off over time by train cars that line up under the funnels in a tunnel below. This technique enabled production to increase dramatically. In World War Two, molybdenum was considered an important strategic resource, as it was used to make hardened steel for everything from aircraft engines to armor plating. Most of the nation’s supply at that time came from this mine. By 1957, Climax claimed to be the largest underground mine in the world. A company town, built here in 1936, had as many as 2,000 people in the 1950s. In the 1960s, as open pit mining expanded, the town was in the way, and was removed, and a popular skiing operation was closed. Many of the town’s buildings, and people, moved to Leadville, joining the rest of the workforce, which surpassed 3,000 employees by 1979. After decades of operating as an underground mine, Climax became a surface mine in the 1960s, further transforming the topography by reshaping mountains, digging pits, and piling tailings, and changing the course of the Divide, in ways that have not really been studied or recorded on maps. In 1976, the more advanced underground operation at the Henderson Mine, up the Divide, opened, and environmental laws were having an effect on the older operations here. By 1982 mining had decreased to a trickle, then stopped altogether a few years later. Though open pit mining started up again in 2012, the emphasis now is mostly about remediation, reclamation, mitigation, and erasure—as much as that might be possible.