Union Slough National Wildlife Refuge was established in 1937 to provide a refuge and breeding ground for
migratory birds and other wildlife. The actual slough is all that remains of a pre-glacial riverbed, and its name
is derived from the connection or "union" of two watersheds: the Blue Earth River of Minnesota and the East Fork of the Des Moines River. The terrain is nearly flat, allowing the flow of the water to be determined by the direction of the wind at times.