From the Fairfax Stone, the North Branch Potomac River flows 27 miles (43 km) to the man-made Jennings Randolph Lake, an impoundment designed for flood control and emergency water supply.

Below the dam, the North Branch cuts a serpentine path through the eastern Allegheny Mountains.

Historically, the North Branch had highly acidic water due to waste from coal mining and paper production in the region.

It was somewhat mitigated by the construction of the Bloomington Dam, which allowed for flow control based on density.

[4] The dam was constructed in 1981; by 1987, the pH had returned to the neutral range in some areas, but dissolved aluminum and manganese concentrations were still at toxic levels, which continued to impede full wildlife recovery.