The Black Hills Flood of 1972, also known as the Rapid City Flood, was the most detrimental flood in South Dakota history, and the second most deadly flood in U.S. history. It took place on June 9–10, 1972 in the Black Hills of Western South Dakota. 15 inches (380 mm) of rainfall over six hours sent Rapid Creek and other waterways overflowing, flooding many residential and commercial properties in Rapid City. It also caused flooding of Battle, Spring, Bear Butte, and Boxelder Creeks.
During the night of June 9, Canyon Lake Dam became clogged with debris and failed, resulting in 238 deaths and 3,057 injuries. Several bodies were never found. Over 1,335 homes and 5,000 automobiles were destroyed. The value of the damaged property was over US $160 million in 1972 dollars ($936 million in 2017 dollars).