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 west of New York City and about 23 miles west of Newark, New Jersey. As of the 2020 United States census, the town's population was 18,460, its highest decennial census count ever and an increase of 303 from the 2010 census count of 18,157, which in turn had reflected a decline of 31 from the 18,188 counted at the 2000 census.