[15] Hillside was created from parcels of land carved out of neighboring Newark, Elizabeth, and Union.

[citation needed] Hillside was incorporated shortly after the appearance of Halley's Comet in 1910, and for that reason, the team nickname of Hillside High School was made the "Comets" when the high school opened in 1940.

[citation needed] The Hillside Historical Society was established in the 1980s in the Woodruff home on Conant Street, perhaps the township's oldest.

The Woodruff House and Eaton Store Museum is operated and maintained by the Hillside Historical Society.

The Woodruff House spans three centuries in one structure, including the original 1735 building, the 1790 addition, the 1890s kitchen and the 1900s store.

Jean-Ray Turner, a reporter for the Elizabeth Daily Journal, wrote Along the Upper Road in the 1970s, a book of the history of Hillside.

Blue collar workers who lived primarily in the central part of town were employed in local manufacturing concerns.

White collar workers established the neighborhood known as Westminster where Yankee shortstop and broadcaster Phil Rizzuto lived for most of his adult life, until his death.

That section of town also included the private Pingry School for boys (which left the township) and is now the East Campus of Kean University.

[26] In the 1950s and 1960s the township was approximately one-half Jewish, many of whom lived either in Westminster or in the area of Hillside near Chancellor Avenue, adjacent to the Weequahic section of Newark, which was the early home of comedian Jerry Lewis and writer Philip Roth (Portnoy's Complaint).

[27] Also in the 1950s the Town Hall, Police Headquarters and Municipal Library were constructed at the corner of Liberty and Hillside Avenues.

Two of the people inside the vehicle were killed and four of the five other passengers were wounded, though the Union County Prosecutor indicated that there was no clear explanation for why the police had started shooting.

[28] The Reverend Al Sharpton held a rally outside Town Hall on Hillside Avenue demanding that the police officers involved in the shootings should be prosecuted for their actions.

[1][2] Unincorporated communities, localities and place names located partially or completely within the township include Lyons Farms and Saybrooke.

[31][32][33] The climate in this area is characterized by hot, humid summers and generally mild to cool winters.

[53] As of 2025[update], the Mayor of Hillside is Dahlia O. Vertreese, whose term of office ends December 31, 2025.

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

[64] For the 2024–2025 session, the 28th legislative district of the New Jersey Legislature is represented in the State Senate by Renee Burgess (D, Irvington) and in the General Assembly by Garnet Hall (D, Maplewood) and Cleopatra Tucker (D, Newark).

[66] As of 2025[update], Union County's County Commissioners are: Rebecca Williams (D, Plainfield, 2025),[67] Joesph Bodek (D, Linden, 2026),[68] James E. Baker Jr. (D, Rahway, 2027),[69] Michele Delisfort (D, Union Township, 2026),[70] Sergio Granados (D, Elizabeth, 2025),[71] Bette Jane Kowalski (D, Cranford, 2025),[72] Vice Chair Lourdes M. Leon (D, Elizabeth, 2026),[73] Alexander Mirabella (D, Fanwood, 2027)[74] and Chair Kimberly Palmieri-Mouded (D, Westfield, 2027).

[75][76] Constitutional officers elected on a countywide basis are: Clerk Joanne Rajoppi (D, Union Township, 2025),[77][78] Sheriff Peter Corvelli (D, Kenilworth, 2026)[79][80] and Surrogate Christopher E. Hudak (D, Clark, 2027).

[83] Among the township's 2010 Census population, 56.0% (vs. 53.3% in Union County) were registered to vote, including 73.4% of those ages 18 and over (vs. 70.6% countywide).

[106] A portion of Kean University is located in the Westminster section of Hillside, on the grounds of the former Pingry School.

Newark Liberty International Airport is approximately 2 miles (3.2 km) east of Hillside.

People who were born in, residents of, or otherwise closely associated with Hillside include: Hillside is the site of Evergreen Cemetery, known locally as the burial site of many Roma (or Gypsy) families and a number of notable writers, including: