In 1869, a catastrophic engineering failure nearly erased St. Anthony Falls, a crucial water source for Minneapolis, Minnesota. The disaster began when the Eastman Tunnel, an ambitious underground waterway designed to power local mills, collapsed beneath the Mississippi River. As water surged through the breach, the falls began to erode, threatening to destroy the region’s primary economic driver. Engineers scrambled to contain the damage, using timber, rocks, and clay to prevent the total collapse of the falls. Their emergency efforts saved St. Anthony Falls from disappearing forever, preserving the city's future. Today, remnants of this near-catastrophe remain hidden beneath the river, a forgotten tale of hubris and survival.