Kenilworth is a borough in Union County, New Jersey, United States. As of the 2010 United States Census, the borough's population was 7,914, reflecting an increase of 239 (+3.1%) from the 7,675 counted in the 2000 Census, which had in turn increased by 101 (+1.3%) from the 7,574 counted in the 1990 Census.
Kenilworth was incorporated as a borough by an act of the New Jersey Legislature on May 13, 1907, from portions of Cranford and Union Township, based on the results of a referendum held on June 18, 1907.
In the late 1890s, the New Orange Industrial Association purchased land in Cranford and Union that was subdivided into building lots. The firm brought in several large industries and lured Upsala College from Brooklyn with an offer of cash and free land for its campus.
Because New Orange was often confused with one of The Oranges in Essex County, the name "Kenilworth" was chosen when the borough was incorporated in 1907. The name Kenilworth came from a literary society (The Kenilworth Club) which the businessmen belonged to. The Kenilworth Club was named in honor of the novel Kenilworth written in 1821 by Sir Walter Scott. The novel refers to England's Kenilworth Castle located in Kenilworth, England.
According to the United States Census Bureau, the borough had a total area of 2.161 square miles (5.598 km2), including 2.157 square miles (5.588 km2) of land and 0.004 square miles (0.010 km2) of water (0.19%).
The upper reaches of Rahway River Parkway along tributaries of the Rahway River run through the borough.
The borough is bordered to the north and east by Union Township, to the southeast by Roselle Park, to the southwest by Cranford, and to the northwest by Springfield Township.
Lenape Park is a 450-acre (180 ha) wildlife reserve and park that is part of the Rahway River Parkway in Union County. The park also includes portions of Cranford, Springfield and Westfield.
The 2010 United States Census counted 7,914 people, 2,841 households, and 2,102.340 families in the borough. The population density was 3,668.3 per square mile (1,416.3/km2). There were 2,924 housing units at an average density of 1,355.3 per square mile (523.3/km2).