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.
As of the census of 2000, there were 23,007 people, 10,027 households, and 6,036 families residing in the borough. The population density was 23,847.7 people per square mile (9,253.2/km). There were 10,375 housing units at an average density of 10,754.1/sq mi (4,172.7/km). The racial makeup of the borough was 77.85% White, 1.83% African American, 0.25% Native American, 12.05% Asian, 0.02% Pacific Islander, 4.97% from other races, and 3.02% from two or more races. Hispanic or Latino of any race were 18.16% of the population.
As of the 2000 census, 3.6% of Cliffside Park's residents identified themselves as being of Armenian-American ancestry. This was the highest percentage in New Jersey, and the seventh highest percentage of Armenian American people in any place in the United States with 1,000 or more residents identifying their ancestry.
There were 10,027 households out of which 21.9% had children under the age of 18 living with them, 46.2% were married couples living together, 9.8% had a female householder with no husband present, and 39.8% were non-families. 33.8% of all households were made up of individuals and 13.8% had someone living alone who was 65 years of age or older. The average household size was 2.29 and the average family size was 2.95.
In the borough the population was spread out with 16.9% under the age of 18, 7.4% from 18 to 24, 33.6% from 25 to 44, 23.8% from 45 to 64, and 18.4% who were 65 years of age or older. The median age was 40 years. For every 100 females there were 93.1 males. For every 100 females age 18 and over, there were 90.6 males.
The median income for a household in the borough was $46,288, and the median income for a family was $54,915. Males had a median income of $40,114 versus $36,100 for females. The per capita income for the borough was $28,516. About 8.5% of families and 10.7% of the population were below the poverty line, including 12.1% of those under age 18 and 10.2% of those age 65 or over.
New Jersey Transit bus lines 156, 159 and 181 offer service to the Port Authority Bus Terminal in Midtown Manhattan; the 22 route serves Jersey City; and the 751, and 755 offer local service.
Palisade Avenue and Anderson Avenue are the main roads of Cliffside Park.