A large part of the township, including the New City Village area, is reservoir property owned by the City of Newark in Essex County for its water supply. Newfoundland is divided by the Pequannock River, which divides Passaic and Morris Counties a small part of Newfoundland lies within Jefferson Township. There are old place names in the township including Postville, Utterville, Corterville, Browns, Awosting, Echo Lake, Macopin, Charlottenburg (now under the Charlotteburg Reservoir, the community was named after Queen Charlotte), Clinton (or sometimes called Clinton Furnace, now under the Clinton Reservoir, and the furnace still stands), Moe Mountain, Oak Ridge (a nameplace, but town is under the Oak Ridge Reservoir), Newfoundland, Apshawa, New City, and Smith Mills. The township was named for Milford, Connecticut. On February 7, 1837, Passaic County was created from portions of both Bergen County and Essex County, with West Milford as the western end of the newly formed county. West Milford became a municipality by an act of the New Jersey Legislature on March 10, 1834, when it was formed from the westernmost half of Pompton Township, while the area was still part of Bergen County. is said to have approved the other application first and assigned the name 'West Milford' to the New Milford in western Bergen County in order to distinguish between the two locations. When both New Milfords applied for post offices in 1828, a clerk in Washington, D.C. These same Dutch also built a town of New Milford in eastern Bergen County. West Milford started out as New Milford in what was then western Bergen County in the 18th century, having been settled by disenchanted Dutch from Milford, New Jersey (later renamed by the British as Newark).

It is the largest in the county by total area, covering 80.32 square miles (208.0 km 2) and more than 40% of the county.

As of the 2020 United States census, the township's population was 24,862, a decrease of 988 (−3.8%) from the 2010 census count of 25,850, which in turn reflected a decline of 560 (−2.1%) from the 26,410 counted in the 2000 census. West Milford is a township in Passaic County, in the U.S.

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