 It joins the Des Moines River in Warren County near Carlisle, southeast of Des Moines.A short headwaters tributary of the river is known as the South Fork Middle River.It rises near the western edge of Guthrie County, about a mile north of Adair, at an elevation of and flows generally east-southeast for about passing just south of Casey before turning northeast as it empties into the Middle River just east of Casey at an elevation of .