Seneca State Forest is located in Pocahontas County, on the Greenbrier River. It includes 11,680 acres and is the oldest unit in the state park and forest system. Most of the land was acquired by the West Virginia Game and Fish Commission in January 1924 with the purchase of 10,847 acres from A. D. Neill.

At that time, the cutting of the virgin timber on the land was nearing completion. The Raine Lumber Company had timber rights when the state bought the property, and continued logging until 1929. The state built a fire tower in its new forest in 1924 and built the first public campground in West Virginia in 1928. Also in 1928, the first state tree nursery was established at Seneca. Civilian Conservation Corps Camp Seneca was established in June 1933, across from the present forest headquarters. By the time the CCC camp was closed in June 1938, access roads, trails, picnic areas, eight cabins, and a lake had been constructed. Reforestation, timber stand improvement, and game and fish management programs were also begun by the CCC enrollees.

The recreation facilities were opened to the public in the summer of 1937 and hunting was allowed the following year. The forest was named for the Seneca Trail, which passed through present Pocahontas County although not through the forest. The Greenbrier River Trail and the Allegheny Trail pass through the forest, while 10 other trails and some logging roads offer 23 miles of hiking and biking opportunities. Available for rent is the restored historic Thorny Mountain Fire Tower, which National Geographic named as one of the nation's "10 places to embrace the wild without pitching a tent."