Elmwood Park, NJ. Online Offers. Elmwood Park is a borough in Bergen County, New Jersey, United States. As of the 2010 census, the borough population was 19,403. Prior to 1916, the area was known as Dundee Lake, a section of Saddle River Township. Residents of the Dundee Lake area voted on April 18, 1916, to secede from Saddle River Township to form the Borough of East Paterson.