The origins of European settlement in Plainfield date from the 1680s when Scots from Perth Amboy established outplantations along the Cedar Brook. English and Scottish Quakers began settling the area in the early 18th century and a Quaker Meeting was formed in 1736. The sparse population numbered less than one hundred in 1770. A second Quaker Meeting House, built in 1788, still stands on what is now Watchung Avenue.

Settlement occurred along Front Street, an old east-west route which ran along the east bank of the Green Brook. This stream also provided the water power for milling which was to become a

major economic activity and focal point of the settlement by the end of the 18th century.

For a time, the settlement was known as Milltown, but by the early 19th century, it became known as Plainfield. The first railroad construction was completed through Plainfield in 1837 by the Elizabethtown and Somerville Railroad. Hat and clothing manufacture became the mainstays of the town’s economy in addition to the mill and shop trade which serviced the surrounding farm communities.

Plainfield was incorporated as a city in 1869, shortly after the rail connection with New York City was completed. Plainfield quickly transformed from a rural village to a fashionable commuter suburb of 12,000 residents. A wave of land development occurred in the 1870s and 1880s, with substantial dwellings for an affluent middle class being built. Today, eight historic districts are listed on the State and National Registers of Historic Places. In the late 19th century, Plainfield was known as the City of Homes, residences built on streets 'under continuous archways of maples and elms'.

People were drawn to Plainfield for its healthful atmosphere, many staying at one of Plainfield’s five resort hotels. In 1886, a New York City newspaper editor compared Plainfield’s climate to that of Denver, Colorado, known as the Queen City of the West. He then dubbed Plainfield as the Queen City of the East, a moniker that remains to this day.

The early 20th century saw the expansion of the central business district. Much residential development of this time period rivaled the scale and grandeur of that dating from the Victorian period. The Sleepy Hollow community, developed off Woodland and Watchung Avenues near the border of Scotch Plains, is noted for fine examples of early 20th century architectural styles. By the mid-1950s, Plainfield had become a shopping Mecca, with many arriving by train. The population of the city evolved as a result of the civil unrest of the late 1960s. Most neighborhoods are thriving with a population that is diverse in age, race, gender and economic standing. The last forty years has brought an influx of people interested in historic preservation, attracted to the city because of its diversity and vintage housing stock dating from the 18th century to the 1930s. Its two commuter stations on the Raritan Valley Line, downtown Plainfield and Netherwood, have undergone beautiful restorations by New Jersey Transit.