At 3:25 pm on June 17, 1937, the Caspian Mine's 60-foot-tall steel No. 2 shafthouse, one of four then standing, dropped out of sight beneath the muddy waters of a pit that suddenly opened beside it, and the wooden No. 3 shaft also fell in from the other side as water rose and covered much of the surrounding area. The 105-foot No. 1 shafthouse reportedly settled only a few inches. No. 2 had taken miners underground, while No. 1 brought iron ore to the surface. Twenty-five men worked frantically to remove equipment and machinery from a nearby machine shop, and three ore cars had crossed a half hour earlier on railroad tracks left suspended above the pit. No one died, unlike the 1893 Mansfield Mine cave-in that killed 27 men and the Amasa Porter Mine disaster that claimed 17 in 1918. Mining at the Caspian had ended in 1931, but ore shipments continued until the cave-in closed operations for good. The Caspian Mine operated from 1900 to 1937. Caspian No. 1, the oldest headframe remaining in Iron County, was built of steel in 1920 to replace the original wooden structure above the 539-foot-deep shaft and was stabilized after the 1937 disaster. Verona Mining Co. operated the mine by the stoping and slicing method, with Pickands-Mather and Co. as agent. The mine shipped 6.6 million tons of ore on the C&NW railroad to Escanaba, where ships carried it to distant steel mills, and Iron County's total production from 1882 to 1978 reached 208 million tons.