Mountainside Borough is on land set aside many years ago by the Lenni-Lenapi Indians as hunting grounds.  It was part of the "West Fields" of Elizabethtown in the 18th century and then part of Westfield Town in the 19th century.  In 1895, the citizens of the area formed the new borough of Mountainside.  Today it is an attractive, residential community featuring an abundance of trees and hilly terrain that bear witness to its name.  Built on the side of the Watchung mountains, Mountainsides's growth since World War II has taken the form of single family homes on streets which wind up the mountain, giving many houses a view across New Jersey to the New York City skyline.   While today there is virtually no unused land in Mountainside, there is a great deal of open space as part of the union County park system.  the commercial center includes several banks, small specialty shops and food stores.