The White River originates East of Harrison, Nebraska, and enters South Dakota in Shannon County.
It continues toward the northeast, then turns east, forming the southern boundary of Lyman County.
It flows through the eastern panhandle into its final destination, the Missouri River. This is on the eastern edge of Lyman County, just south of the town of Oacoma.
 | The elevation of the White River drops an average of 3.9 feet per mile in Lyman County. |
| There are many creeks that drain into the White River. |
| The Little White River joins the White River between the towns of Murdo and White River, South Dakota. This is just outside the western border of Lyman County. |
| The latitude of the White River in Lyman County is North 43 degrees. |