Cliffside Park is a borough in Bergen County, New Jersey, United States. As of the 2010 United States Census, the borough's population was 23,594, reflecting an increase of 587 (+2.6%) from the 23,007 counted in the 2000 Census, which had in turn increased by 2,614 (+12.8%) from the 20,393 counted in the 1990 Census.
Cliffside Park was formed based on the results of a referendum held on January 15, 1895, from portions of Ridgefield Township. The borough was formed during the "Boroughitis" phenomenon then sweeping through Bergen County, as of one two boroughs created in 1895 after 26 boroughs were formed in the county in 1894 alone.
U.S. Senator Frank Lautenberg resided in the borough until his death in 2013. Cliffside Park was home to the former Palisades Amusement Park, part of which was located in adjoining Fort Lee. The park operated from 1898 until 1971, remaining one of the most-visited amusement parks in the country until its closure, after which the rides and attractions were removed and the site replaced by high-rise apartment buildings.