Dover is a town in Morris County, in the U.S. state of New Jersey. Located on the Rockaway River, Dover is about 31 miles (50 km) west of New York City and about 23 miles (37 km) west of Newark, New Jersey. As of the 2020 United States census, the town's population was 18,460, an increase of 303 (+1.7%) from the 2010 census count of 18,157, which in turn reflected a decline of 31 (−0.2%) from the 18,188 counted in the 2000 census.

The Rockaway River is a tributary of the Passaic River, approximately 35 mi (56 km) long, in Morris County, New Jersey in the United States. The upper course of the river flows through a wooded mountainous valley, whereas the lower course flows through the populated New Jersey suburbs and former industrial area west of New York City. It drains an area of approximately 130 sq mi (340 km²).