Lake Elmo is a popular 64-acre urban fishing destination located within Billings city limits in Yellowstone County, Montana. This artificial reservoir, managed as Lake Elmo State Park, serves as both an irrigation water source and a heavily utilized recreational fishery that consistently ranks among Montana's most visited state parks. The lake features a maximum depth suitable for both warm and coldwater species, with excellent bank fishing opportunities, a concrete boat ramp, and the notable Rogers Pier on the south shore. While currently supporting diverse fish populations including both stocked trout and established warm water species, the lake has faced significant aquatic invasive species challenges, including a major eradication effort for Asian clams (Corbicula fluminea) discovered in 2019 that required a complete drawdown and refill in 2021-2022.