[2] Freeman Run joins the First Fork at the community of Costello, Potter County.
The East Fork joins 5.6 miles (9.0 km) downstream at the community of Wharton, Potter County.
The First Fork continues for 11.8 miles (19.0 km) to the George B. Stevenson Dam in Sinnemahoning State Park.
[2] The dam creates the George B. Stevenson Reservoir, a 142-acre (57 ha) lake constructed by the Commonwealth of Pennsylvania in 1955 as part of the flood control project on the West Branch Susquehanna River.
These four reservoirs and dams control a total of 1,163 square miles (3,010 km2) of drainage area and provide flood prevention for the cities and towns downstream.