Falls Run begins in a valley on Buck Mountain in Beaver Township, Columbia County.

It flows east for more than a mile in the valley before exiting Beaver Township and Columbia County.

After several tenths of a mile, the stream turns northeast, leaving the mountain and entering the community of Rock Glen.

It then turns north, leaving Rock Glen and flowing alongside Black Creek.

[2] Falls Run is one of eleven officially named streams in the watershed of Nescopeck Creek that has not been assessed by the Pennsylvania Fish and Boat Commission.

[3] In the early 1900s, Falls Run was used as a water supply for the village of Rock Glen, a mining community that had a population of approximately 300 people at the time.