The Great Allegheny Passage is part of a trail system connecting Pittsburgh, Pennsylvania, to Washington, D.C. Conceived in 1975, the 150-mile-long Passage connects to the C&O Canal Towpath in Cumberland, Maryland, and together they form a significant segment of the Potomac Heritage National Scenic Trail within the National Trail System. Nearby, Connellsville lay 17 miles west, where coal-converting coke ovens made fuel for the region's steel mills and the town thrived; East Park, built in the 1930s, is a Works Project Administration undertaking. The Sheepskin Trail, 15 miles west, leads 2.2 miles to Dunbar, where Dunbar Creek and Gist Run converge, and future construction will extend the trail more than 40 miles to Morgantown; the junction called Bowest was where the B&O and Western Maryland railroads intersected. Ferncliff Peninsula, 0.25 miles west, was created by a sharp bend in the Youghiogheny River, with steep rocky ledges forming Ohiopyle Falls; designated a National Natural Landmark, it contains an oak forest and many rare plants, and the trail crosses its neck and the river twice in less than half a mile. Twelve miles east, the Youghiogheny Dam, 1,610 feet long, creates a 16-mile lake and was built in 1943 by the U.S. Army Corps of Engineers to control flooding in Pittsburgh after the St. Patrick's Day Flood of 1936. Ten miles east, Confluence stands at the meeting of the Casselman River, Laurel Hill Creek, and the Youghiogheny River. Twenty miles east, the 849-foot Pinkerton Tunnel passes through the Pinkerton Horn, a narrow peninsula formed by a hairpin bend in the Casselman River; built in 1911 for the Western Maryland Railway, it was rehabilitated and reopened to bicycle and foot traffic in 2015, and its corrugated liner is unique along the Great Allegheny Passage.