The Red River, 100 miles long, is a major stream of north-central Tennessee and south-central Kentucky, and a major tributary of the Cumberland River. It rises in Sumner County, Tennessee, south of Portland. Trending generally northwest, it is crossed by several roads, notably State Route 76, U.S. Route 31W, and Interstate 65. A major t…The Red River, 100 miles long, is a major stream of north-central Tennessee and south-central Kentucky, and a major tributary of the Cumberland River. It rises in Sumner County, Tennessee, south of Portland. Trending generally northwest, it is crossed by several roads, notably State Route 76, U.S. Route 31W, and Interstate 65. A major tributary, the South Fork, forms nearby and runs parallel and south of the main river for several miles. For almost its entire length, it drains the northern Highland Rim of Tennessee and the adjacent Pennyroyal Plateau of Kentucky.