Hillside is a township

Township (New Jersey)

A township, in the context of New Jersey local government, refers to one of five types and one of eleven forms of municipal government. As a political entity, a township is a full-fledged municipality, on par with any town, city, borough, or village, collecting property taxes and providing...

 in Union County

Union County, New Jersey

Union County is a county located in the U.S. state of New Jersey. As of the 2010 Census, the population was 536,499. It is part of the New York Metropolitan Area. Its county seat is Elizabeth. Union County ranks 93rd among the highest-income counties in the United States. It also ranks 74th in...

, New Jersey

New Jersey

New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...

, United States. As of the 2010 United States Census, the township population was 21,404.

Hillside was incorporated as a township on April 3, 1913, from portions of Union Township

Union Township, Union County, New Jersey

Union is a Township in Union County, New Jersey, United States. In the 18th century, the area that is now Union was then called Connecticut Farms...

, based on the results of a referendum held on April 29, 1913.

The town is split between area codes 908

Area code 908

Area code 908 is an area code in northern New Jersey. The area code covers the North/Central portions of the state. It includes communities in Union County, Somerset County, northern parts of Middlesex County, Hunterdon County, Warren County, and Morris County as well as some cell phones in...

 and 862/973

Area codes 862 and 973

Area code 973 is a North American Numbering Plan area code for Northern New Jersey that covers portions of Bergen, Essex, Hudson, Morris, Passaic, Sussex and Union Counties. It was formed as of June 1, 1997 when Area code 201 was split. In 2001, the 862 area code was created to overlay the 973...

.
Hillside is located at 40.695552°N 74.228561°W (40.695552, -74.228561).

The township is located on the northern edge of Union County and is bordered to the northwest by Irvington

Irvington, New Jersey

Irvington is a township in Essex County, New Jersey, United States. As of the 2010 United States Census, the township had a total population of 53,926, a decline of 11.2% from the 60,695 residents enumerated in the 2000 Census.-Geography:...

 and to the north and northeast by Newark

Newark, New Jersey

Newark is the largest city in the American state of New Jersey, and the seat of Essex County. As of the 2010 United States Census, Newark had a population of 277,140, maintaining its status as the largest municipality in New Jersey. It is the 68th largest city in the U.S...

, both in Essex County

Essex County, New Jersey

Essex County is a county located in the northeastern part of the U.S. state of New Jersey. As of the United States 2010 Census, the population was 783,969, ranking it third in the state after Bergen County and Middlesex County; Essex County's population has declined from 786,147 as of the bureau's...

.