Minneopa State Park is a state park in Minnesota, United States, and was established in 1905 to preserve Minneopa Falls. Located on Minneopa Creek and being the largest waterfall in southern Minnesota, the site has been a popular visitor attraction since the 1850s. Minneopa is Minnesota's third oldest state park, after Itasca and Interstate. Two park resources are listed on the National Register of Historic Places: the 1862 Seppman Mill and a district of seven Rustic Style structures built by the Works Progress Administration in the late 1930s. The park is located almost entirely on the southern side of the Minnesota River 3 miles (4.8 km) west of Mankato.