Mann Wilderness Area is a rugged forested area along the Iowa River Greenbelt. This 103-acre preserve is located five miles north of Steamboat Rock in northeastern Hardin County. The Hardin County Conservation Board purchased the rugged area from Joe and Flossie Mann in 1960. It was dedicated as a biological and geological state preserve in 1979.

Located near the eastern edge of the Des Moines Lobe landform region, the topography of this preserve is dominated by a long, narrow ridge paralleled by deep ravines draining into the entrenched course of the Iowa River, which forms most of the preserve’s southern border. This highly dissected landscape was formed by downcutting streams that eroded through soft glacial deposits to the underlying limestone bedrock. Rugged topography with frequent outcrops of these Mississippian (350-million-years-old) limestones along the valley walls contribute to the scenic character of the Iowa River Greenbelt.