[21] 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.

[22] 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.

Area residents have proposed a 7.3-mile pedestrian linear park along the "main line" of the abandoned Rahway Valley Railroad that would run through Kenilworth.

[31][32] The rail trail would run eastbound from Overlook Medical Center on the edge of downtown Summit and head south through Springfield, Union, over Route 22 to Kenilworth.

[33][34] In parallel, advocates have been pushing for immediate development of the portion of the RVRR Main Line south of Route 22, running past the Galloping Hill Golf Course through Kenilworth and Roselle Park.

The New Jersey Department of Transportation, which owns the railbed, has been working to clear it in anticipation of possible future trail use for pedestrians and cyclists.

[44] Merck & Co. announced plans in October 2013 to move its global headquarters to Kenilworth from Whitehouse Station in Readington Township, on a site that the company had previously used as a manufacturing facility, with the relocation to be completed by 2015.

The Friends of the Kenilworth Library, with the assistance of a grant from the Union County Office of Cultural Affairs, sponsor these events.

[50][51] As of 2025[update], the mayor of Kenilworth is Democrat Linda Karlovitch, serving a four-year term of office ending December 31, 2027.

[52][3][53][54][55][56] In August 2020, the borough council appointed Louis DeMondo to fill the seat expiring in December 2021 that had been vacated the previous month following the resignation of Robert Schielke.

[58] In May 2016, the borough council again appointed Scott Pentz, this time to fill the seat expiring in December 2016 that had been vacated by Brian Joho when he resigned from office.

[59] In January 2016, the borough council appointed former councilmember Lawrence Clementi to fill the seat expiring in December 2017 that had been held by Anthony DeLuca, until he resigned from the council to take office as mayor; Clementi will serve on an interim basis until the November 2016 general election, when voters will choose a candidate to serve the balance of the term of office.

[60] In July 2015, the borough council selected Scott Pentz from a list of three candidates nominated by the Republican municipal committee to fill the seat expiring in December 2016 that had been held by Barbara Macecsko, until she resigned from office the previous month.

[62] Mayor Kathi Fiamingo resigned her position in April 2014 after being selected to serve as a tax court judge.

[67] For the 119th United States Congress, New Jersey's 10th congressional district is represented by LaMonica McIver (D, Newark).

[69] For the 2024-2025 session, the 20th legislative district of the New Jersey Legislature is represented in the State Senate by Joseph Cryan (D, Union Township) and in the General Assembly by Reginald Atkins (D, Roselle) and Annette Quijano (D, Elizabeth).

[71] As of 2025[update], Union County's County Commissioners are: Rebecca Williams (D, Plainfield, 2025),[72] Joesph Bodek (D, Linden, 2026),[73] James E. Baker Jr. (D, Rahway, 2027),[74] Michele Delisfort (D, Union Township, 2026),[75] Sergio Granados (D, Elizabeth, 2025),[76] Bette Jane Kowalski (D, Cranford, 2025),[77] Vice Chair Lourdes M. Leon (D, Elizabeth, 2026),[78] Alexander Mirabella (D, Fanwood, 2027)[79] and Chair Kimberly Palmieri-Mouded (D, Westfield, 2027).

[80][81] Constitutional officers elected on a countywide basis are: Clerk Joanne Rajoppi (D, Union Township, 2025),[82][83] Sheriff Peter Corvelli (D, Kenilworth, 2026)[84][85] and Surrogate Christopher E. Hudak (D, Clark, 2027).

[88] Among the borough's 2010 Census population, 61.8% (vs. 53.3% in Union County) were registered to vote, including 79.1% of those ages 18 and over (vs. 70.6% countywide).

CR 509 (Boulevard) runs west–east through the borough, connecting it to Cranford, Springfield and Westfield in one direction and Union and Roselle Park in the other.

[114] The Rahway Valley Railroad passed through the community but is currently out of service, the final train on the line having left the borough in April 1992.

Originally established as the New York and New Orange Railroad, the line stretched 11.8 miles (19.0 km) from Aldene (now known as Roselle Park) to Summit.