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is a township in Union County, New Jersey, United States. As of the United States 2000 Census, the township population was 21,747.
Hillside was incorporated as a township on April 3, 1913, from portions of Union Township, based on the results of a referendum held on April 29, 1913.
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.
According to the United States Census Bureau, the township has a total area of 2.8 square miles (7.2 km