North Caldwell is a borough in northwestern Essex County, New Jersey, United States, and a suburb of New York City. As of the 2010 United States Census, the borough's population was 6,183, reflecting a decline of 1,192 (−16.2%) from the 7,375 counted in the 2000 Census, which had in turn increased by 669 (+10.0%) from the 6,706 counted in the 1990 Census.
North Caldwell was incorporated by an act of the New Jersey Legislature on March 31, 1898, from portions of Caldwell Township (now known as Fairfield Township). The borough derives its name from Presbyterian minister James Caldwell.
New Jersey Monthly magazine ranked North Caldwell as its 10th best place to live in its 2010 rankings of the "Best Places To Live" in New Jersey, as well as the 3rd best place to live in its 2013 ranking. In 2017, a Bloomberg analysis ranked North Caldwell the 34th richest town in the United States.
North Caldwell was part of the Horseneck Tract, which was an area that consisted of what are now the municipalities of Caldwell, West Caldwell, North Caldwell, Fairfield, Verona, Cedar Grove, Essex Fells, Roseland, and portions of Livingston and West Orange. In 1702, settlers purchased the 14,000 acres (57 km2) from the Lenape Native Americans for goods equal to $325. The explanation for the name "Horse Neck" lies in the language of its first Dutch settlers and not (as has been inaccurately reported) because of its irregular shape. This purchase encompassed much of western Essex County, from the First Mountain to the Passaic River.
In 1982, the borough was one of four Essex County municipalities to pass a referendum to become a township, joining 11 municipalities that had already made the change. Ultimately, more than a dozen Essex County municipalities reclassified themselves as townships in order take advantage of federal revenue sharing policies that allocated townships a greater share of government aid to municipalities on a per capita basis. Effective January 1, 1992, it again became a borough.
The borough housed the Essex County Penitentiary, constructed in 1872 and used as the Essex County Jail Annex until 2004. It was sold to K. Hovnanian Companies in 2002, which redeveloped the site into a residential community.
In 1994, the "Unabomber", Theodore Kaczynski, sent a mail bomb that killed Thomas J. Mosser, an advertising executive who lived in the borough.
According to the United States Census Bureau, the borough had a total area of 3.07 square miles (7.96 km2), including 3.07 square miles (7.95 km2) of land and 0.01 square miles (0.01 km2) of water (0.16%).