Riverdale is a borough in Morris County, New Jersey, United States. As of the 2010 United States Census, the borough's population was 3,559, reflecting an increase of 1,061 (+42.5%) from the 2,498 counted in the 2000 Census, which had in turn increased by 128 (+5.4%) from the 2,370 counted in the 1990 Census.
Riverdale was incorporated as a borough by an act of the New Jersey Legislature on March 12, 1923, from portions of Pequannock Township, subject to the results of a referendum passed on April 17, 1923.
According to the United States Census Bureau, the borough had a total area of 2.087 square miles (5.403 km2), including 2.015 square miles (5.218 km2) of land and 0.072 square miles (0.185 km2) of water (3.43%).
The borough is bordered by the municipalities of Butler and Kinnelon to the west and by Pequannock Township to the south, all in Morris County; and by Bloomingdale to the north and Pompton Lakes to the east in Passaic County.
The 2010 United States Census counted 3,559 people, 1,547 households, and 917.371 families in the borough. The population density was 1,766.5 per square mile (682.0/km2). There were 1,657 housing units at an average density of 822.5 per square mile (317.6/km2). The racial makeup was 89.86% (3,198) White, 1.21% (43) Black or African American, 0.06% (2) Native American, 5.31% (189) Asian, 0.00% (0) Pacific Islander, 1.66% (59) from other races, and 1.91% (68) from two or more races. Hispanic or Latino of any race were 7.19% (256) of the population.
Of the 1,547 households, 22.7% had children under the age of 18; 48.7% were married couples living together; 7.2% had a female householder with no husband present and 40.7% were non-families. Of all households, 33.2% were made up of individuals and 10.4% had someone living alone who was 65 years of age or older. The average household size was 2.30 and the average family size was 3.01.
18.8% of the population were under the age of 18, 6.2% from 18 to 24, 32.9% from 25 to 44, 27.1% from 45 to 64, and 15.0% who were 65 years of age or older. The median age was 40.0 years. For every 100 females, the population had 96.0 males.