Niagara Falls "ran dry" in 1969 specifically on the American Falls side due to a massive engineering project led by the U.S. Army Corps of Engineers. From June to November of that year, the water was artificially diverted to the Canadian Horseshoe Falls via a temporary 600-foot cofferdam. The primary goal was to conduct a geological study of the rock face. Engineers wanted to determine if they could remove the "talus"—the massive pile of broken rock at the base of the falls—to enhance the waterfall's aesthetic beauty and prevent further erosion that threatened to turn the falls into a series of rapids. Ultimately, they decided the rock was providing vital structural support and that the cost was too high, so the dam was breached in November 1969, and the water returned. The "dry falls" became a unique tourist attraction in its own right, as visitors walked on the dried riverbed and discovered decades of tossed coins and lost items.