The Tug Fork of the Big Sandy River forms the southwestern border of West Virginia for nearly 90 miles, flowing between the West Virginia counties of Mingo and Wayne and neighboring counties in Virginia and Kentucky. The stream, locally known as the Tug River, originates near the town of Jenkinjones at the corner of Mercer and McDowell counties and Tazewell County, Virginia, at an elevation of 2,450 feet. The Tug travels 126 miles in a northwesterly direction to Fort Gay. There it joins the Levisa Fork out of eastern Kentucky to form the main Big Sandy River.

In addition to Jenkinjones, McDowell County settlements along the Tug Fork include Gary, Welch, Davy, Roderfield, Iaeger, and Panther. From McDowell, the stream flows north through Mingo County, by Matewan, Williamson, Chattaroy, Nolan, and Kermit, then past the Wayne County communities of Crum, Glenhayes, and Fort Gay. The Tug forms the western boundary of Mingo and part of the western boundary of Wayne County.

The topography at the headwaters is rugged. The Tug and its tributaries have cut their channels through the sedimentary strata to produce high hogback ridges and deep V-shaped valleys. Local relief, the distance from the valley floors to the hill crests, ranges from 1,200 to 1,500 feet in McDowell County and from 600 to 1,000 feet in Mingo. Elevation above sea level at Fort Gay is 600 feet, yielding a fall of 1,875 feet along the stream's 26 miles, for an average of about 15 feet per mile. This gives the Tug Fork a rapid flow, especially in McDowell County where the rapids and falls include one section known as "the Roughs of the Tug."

The Tug Valley, one of the most remote areas of West Virginia, was among the last places in the state to be settled. Permanent settlement began about 1800, and the region was sparsely populated until the development of the coal industry nearly a century later. The Hatfields, whose later feud with the McCoys is the most notorious event in Tug Valley history, were among the first settlers. Violent labor warfare rocked the valley during the early 20th century. It was at this time that the area's rich coalfields were developed, and mining continues to be the major industry.

The Tug Fork has flooded numerous times since first settlement. Historically, the river was used at flood stage to transport rafts and logs down to Kenova. Under favorable conditions merchandise was poled upriver from Kenova to Williamson in push boats.

On April 5, 1977, the Tug Fork at Williamson reached a record 52.56 feet, more than 25 feet above flood stage. Eleven counties were declared major disaster areas.

The river is believed to have been named in 1756, during Maj. Andrew Lewis's disastrous "Sandy Creek" expedition against the Shawnee Indians in southern Ohio. Near the headwaters, the group attempted to descend the Tug River to Ohio by using canoes for the trip, but they encountered tremendous rapids and lost their supplies. The men were forced to boil and eat their boot strings or "tugs" made of buffalo hides.