Cottonwood River, one of the principal tributaries of the Neosho, is formed by the union of two branches known as the north and south forks. The north fork rises near the west line of Marion county, in township 30 south, range 1 east. It first flows southeast, crossing the east line of Marion county about 12 miles north of the southeast corner, and thence northeast to Cottonwood Falls, Chase county. The south fork rises in the northwest corner of Greenwood county and flows northward until it joins the north fork a short distance below Cottonwood Falls. The main stream then follows an easterly course until it falls into the Neosho a few miles east of Emporia.