Mormon Trail Lake Dam, located in Mt. Etna, Iowa, is a recreational earth dam completed in 1965 with a height of 46 feet and a length of 928 feet. The dam serves the primary purpose of recreation, providing a surface area of 33 acres for water enthusiasts to enjoy. Owned by the local government and regulated by the Iowa DNR, the dam has a low hazard potential and is in satisfactory condition as of the last assessment in December 2014.

The dam impounds water from the TR-West Fork Nodaway River, creating a reservoir with a normal storage capacity of 394 acre-feet and a maximum storage of 585 acre-feet. With a drainage area of 0.65 square miles, the dam has an uncontrolled spillway with a width of 4 feet. Despite being constructed over five decades ago, Mormon Trail Lake Dam still meets modern regulatory standards for inspection, permitting, and enforcement. With a moderate risk assessment rating of 3, the dam is actively monitored to ensure the safety and security of the surrounding community and environment.