Originally inhabited by Indians, Plainfield, New Jersey, has a rich and progressive history.  Watchungs, of the Lenni-Lenape tribe (Delaware) roamed the Green Brook and Watchung areas.  The main streets in Plainfield as well as the railroad track laid in the 1800's followed original Indian trails.  The Revolutionary period saw a fort built here, but it wasn't until April 1, 1800, that a post office was established.  Plainfield was named for the gently swelling hills and fields.

Plainfield is in the westernmost section of Union County, 24 miles southwest of New York City, and considered part of the Greater New York area. Plainfield is a hub for the bordering communities of Dunellen, Piscataway, South Plainfield, Edison, Scotch Plains, Fanwood, and the Somerset communities of Watchung, North Plainfield and Green Brook Township. A cultural leader, as well as a financial leader, Plainfield boasts six lovely historic districts encompassing fine Victorian residences along tree lined streets and excellent examples of 17th Century and Colonial Revival architecture. The Plainfield Symphony is the oldest community symphony orchestra in the state.

Plainfield (approximately six square miles in area), is 100 to 200 feet above sea level. A business-friendly attitude on the part of the City's Administration extends to listing over $150 Million  of City Projects and their status on the web.  The dedicated hard work of the corps of citizen volunteers who serve on the Planning and Zoning Boards is making Plainfield a premier development destination in central New Jersey

The city's population grew from 215 in 1800 to 46,567 in 1990.