The township is located on the northern edge of Union County and is bordered to the northwest by Irvington and to the north and northeast by Newark, both in Essex County. Elizabeth borders Hillside to the east and southeast, while Union borders to the west.
There were 7,161 households out of which 36.0% had children under the age of 18 living with them, 53.5% were married couples living together, 18.8% had a female householder with no husband present, and 22.1% were non-families. 18.0% of all households were made up of individuals and 7.7% had someone living alone who was 65 years of age or older. The average household size was 3.04 and the average family size was 3.45.
In the township the population was spread out with 25.6% under the age of 18, 8.9% from 18 to 24, 30.3% from 25 to 44, 24.1% from 45 to 64, and 11.1% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 88.3 males. For every 100 females age 18 and over, there were 84.2 males.
The median income for a household in the township was $59,136, and the median income for a family was $64,635. Males had a median income of $39,439 versus $31,817 for females. The per capita income for the township was $21,724. About 3.2% of families and 5.3% of the population were below the poverty line, including 5.4% of those under age 18 and 9.1% of those age 65 or over.
Hillside was incorporated shortly after the appearance of Halley's Comet in 1910, and for that reason, the team nickname of Hillside High School is the "Comets." Several local businesses take the name "Comet" for the same reason. The Hillside Historical Society was established in the 1980s in the Woodruff home on Conant Street, perhaps the township's oldest. 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.
Hillside has been the home of Bristol-Myers Squibb and for years was the site of the Lionel Trains factory. The town thrived for decades and reached an economic peak in the 1960s. 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. That section of town also included the private Pingry School for boys, which became co-ed in 1974.
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. This section of Newark was the early home of comedian Jerry Lewis and writer Philip Roth ("Portnoy's Complaint").
In the early 1950s the township established Conant Park, its largest. The park is bounded by the Elizabeth River and Conant Street. At the rear area of the park near Pingry School was the boundary of the Kean Estate, the boyhood home of Governor Thomas Kean (1982-1990). The wealthy Kean family also donated the land on Morris Avenue and helped to establish Newark Normal College in 1885, which has been renamed Kean University in the family's honor. Also in the 1950s the Town Hall, Police Headquarters and Municipal Library were constructed at the corner of Liberty and Hillside Avenues.
Popular township organizations included Rotary, Kiwanis, Knights of Columbus, Elks, the Hillside Industrial Association, the Hillside Business and Professional Women's Club, the Republican Club and the Democratic Club, as well as a number of ethnic clubs and associations.
In the eighties, following an issue with the Hillside Police Department, the Reverend Al Sharpton held a rally outside Town Hall on Hillside Avenue.
In many ways Hillside was a microcosm of the political, economic and sociological forces that shaped America in the post World War II era. These included the original baby-boomers in the 1950s, the abandonment of the township in the 1970s by both the baby-boomers and their parents, the simultaneous settlement and integration by blacks following the Newark race riots in the 1960s, the influx of Hispanic and Portuguese in the 1980s, the rise and fall of the manufacturing-based local economy and more.
The Mayor of Hillside is Karen McCoy Oliver. The members of the Hillside Township Council are:
Catholic grammar schools included Christ the King on Columbia Ave and St. Catherine's of Sienna School in Elizabeth on North Broad Street until the two were merged in 2004 to form Hillside Catholic Academy, with the students from both schools together at the facility on Bloy Street.
Newark Liberty International Airport is approximately four miles east of Hillside.
Garden State Parkway, U.S. Route 22, and Interstate 78 are located in Hillside. A toll gate is located on the northbound lanes of the parkway, approaching the interchange for 78. At the present time, the interchange between 78 & the parkway is lacking certain ramp movements due to the cancellation of Interstate 278. This is to be corrected by 2012.