Linden, city (1990 pop. 36,701), Union co., NE N.J., in the New York metropolitan area; inc. 1925. During the first half of the 20th cent., Linden changed from an agricultural district to a city of diverse manufactures, including chemicals, petroleum products, plastics, advertising signs, and transportation equipment. The city, named for the linden trees in the vicinity, was part of Elizabeth until 1861.