Rapid City is the second most populous city in South Dakota after Sioux Falls and the county seat of Pennington County. Named after Rapid Creek, where the settlement developed, it is in western South Dakota, on the Black Hills' eastern slope. The population was 74,703 as of the 2020 census.

The Black Hills Flood of 1972, also known as the Rapid City Flood, was the most detrimental flood in South Dakota history, and one of the deadliest floods in U.S. history. The flood took place on June 9–10, 1972 in the Black Hills of Western South Dakota. 15 inches (380 mm) of rain in a small area over the Black Hills caused Rapid Creek and other waterways to overflow. Severe flooding of residential and commercial properties in Rapid City occurred when Canyon Lake Dam became clogged with debris and failed in the late evening hours of June 9 resulting in 238 deaths and 3,057 injuries. Over 1,335 homes and 5,000 automobiles were destroyed. The value of property damage was estimated to be over US$160 million in 1972 dollars. Flooding also occurred in Battle, Spring, Bear Butte, and Boxelder creeks.