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It rises in eastern Sussex County, near Highland Lakes on the north side of Hamburg Mountain. It flows southeast to Stockholm, then east-southeast, in a gap north of Green Pond Mountain and other ridges, past Butler and Bloomingdale. It joins the Ramapo River at Pompton Plains in Pequannock Township to form the Pompton.
It is impounded near its source to form the Oak Ridge Reservoir. The river is relatively unspoiled compared to other rivers in the region. It is a popular spot for recreation trout fishing in its upper reaches. Fishing, hunting, and other recreational uses of the river and watershed are controlled by the City of Newark's Division of Watershed Development, which requires permits for all such uses.