High Quality Content by WIKIPEDIA articles! Clark is a township in southern Union County, New Jersey, United States. As of the United States 2000 Census, the township population was 14,597.The territory that would become Clark was originally a part of several of the early villages of the State and of Union County, but it was in 1858 after the village of Rahway incorporated itself into a city, that the land of present-day Clark, officially became a community. The City of Rahway designated this land as the 5th Ward of Rahway. Clark was incorporated as a township by an Act of the New Jersey Legislature on March 23, 1864, from portions of Rahway. The Township was named for Abraham Clark, a signer of the Declaration of Independence. Portions of the township were taken to form Cranford Township (March 14, 1871) and Winfield Township (August 6, 1941).