Mill Creek overflowed into Walla Walla and College Place on March 31, 1931, causing $1 million in damages. Community volunteers jury-rigged makeshift levees to divert water from buildings during the cleanup which cost roughly $100,000. The United States Army Corps of Engineers built the Mill Creek Dam and Bennington Lake in response to the disaster. The dam and lake were instrumental in preventing damage from flooding in 1964, 1996, and 2020.