Only a few years after the Homestake Gold mine began operations in 1876, the residents of Lead, South Dakota, realized they had a problem with their town's location. By the mid-1890s, building foundations were shifting noticeably, and even solidly-built brick structures were showing major cracks and other problems.
Homes and most of Lead's business district had been built close to and even on top of the mine. Years of digging shafts and drifts directly beneath the town, coupled with inadequate attention to precautions like back-filling mined-out spaces, had put the town's very existence in jeopardy.
The video above describes Lead's slow-moving subsidence disaster. The problem was becoming severe at a time when Homestake was struggling to stay in business.