Riverside is a census-designated place (CDP) in Harford County, Maryland, United States. The population was 6,425 at the 2010 census. The term "Riverside" is generally used interchangeably with "Belcamp"; both names are accepted for the U.S. Postal Service's ZIP Code of 21017. However, the original community of Belcamp is located south of U.S. Route 40, outside the Riverside CDP.