Dover is a town in Morris County, New Jersey, United States. 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 2010 United States Census, the town's population was 18,157, reflecting a decline of 31 (-0.2%) from the 18,188 counted in the 2000 Census, which had in turn increased by 3,073 (+20.3%) from the 15,115 counted in the 1990 Census.