The North River basin drains 381 square miles (243,857 acres) of northeastern Missouri covering parts of five counties (Knox, Shelby, Monroe, Marion, Ralls; Figure Lo01). The North River originates in Knox County and flows southeast approximately 78 miles before entering the Upper Mississippi River at River Mile 321. Major tributaries of North River include South Fork, Tiger Fork, and Mesner Branch. South Fork North River originates in Shelby County and flows northeast about 18 miles before its confluence with the main stem in Marion County. Major tributaries of South Fork include Sees Creek and Sharpsburg Branch. Tiger Fork begins in Shelby County and flows southeast about 18 miles before joining the North River.
The North River watershed is bounded by the Fabius River watershed to the north and the Salt River watershed to the south and west.