The Susquehannock Trail System (STS) is a loop hiking trail approximately 85 miles long located in southern Potter and northern Clinton counties in Northcentral Pennsylvania. The region in which the STS is located is a broad plateau dissected by numerous deep valleys. It is classic erosion topography, not true mountains. As you proceed south from the Northern Gateway, the terrain fits the lyrics of the old Appalachian Mountain song, "From here on up the hills don't get any higher; the hollows get deeper and deeper." The area is one of the most lightly-populated sections of Pennsylvania. Elevations along the trail range from 1,056 to 2,561 feet above sea level. Despite the ruggedness of the terrain, the old Civilian Conservation Corps trails (which the trail system is chiefly comprised of) provide some of the easiest hiking of any trail in the state. There are only a few steep climbs, and only one of them is long.

The trail is marked with standard Appalachian Trail-type 2-by-6-inch rectangular orange paint blazes, with the "STS" emblem painted on trees at intervals. The STS is connected to the Black Forest Trail via the North Link and South Link Trails, and for 8.7 miles it shares a path with the Donut Hole Trail. Along its lengthy route, the STS passes few signs of modern civilization and reaches into very remote state forest areas with a particular sense of quietude and seclusion. The longest roadless stretch is ten miles through the Hammersley Wild Area, the state's second largest wild area at 30,253 acres, and is thought to be the largest area without a road in Pennsylvania.