Cliffside Park is a borough in Bergen County, New Jersey, United States. As of the United States 2000 Census, the borough population was 23,007. Cliffside Park was formed based on the results of a referendum held on January 15, 1895, from portions of Ridgefield Township at the start of the second year of the Boroughitis phenomenon then sweeping through Bergen County. U.S. Senator Frank Lautenberg currently resides in the borough. Cliffside Park was also home to the former Palisades Amusement Park.