The route runs northeast through more rural areas, crossing into Slippery Rock Township. Farther northeast, PA 108 heads into the borough of Slippery Rock and becomes New Castle Street, passing through wooded areas of homes.
Northeast along the route, it traverses more rural regions before entering Slippery Rock Township. Further on, PA 108 becomes New Castle Street as it enters the borough of Slippery Rock and moves through wooded neighborhoods with homes.