[21] Greenwich Township has at various times been a part of most of Northwestern New Jersey's counties.

The township was first mentioned in official documents on October 9, 1738, as a part of Hunterdon County.

On June 8, 1753, Sussex County was created, and Greenwich Township was shifted again.

It found its current home when Warren County was formed on November 20, 1824.

On March 7, 1851, Phillipsburg was created from parts of Greenwich, and Pohatcong Township went off on its own as of January 1, 1882.

[27][28][29] Other unincorporated communities, localities and place names located partially or completely within the township include Coopersville, Kennedy Mills, Port Warren and Still Valley.

[31][32] The 2010 United States census counted 5,712 people, 1,808 households, and 1,546 families in the township.

[3][47][48][49][50] In January 2022, the Township Committee appointed Bill Kanyuck to fill the seat expiring in December 2023 that had been held by Frank Marchetta until he resigned from office.

[51] The Township Committee had three vacancies in September 2015, after Tom Callari announced that he was moving out of the township, Joe Tauriello left office after a DUI arrest was made public and Angelo Faillace resigned in protest of the process of selecting a council replacement.

In November 2015, Deputy Mayor Elaine Emiliani resigned from office and was replaced by Frank Marchetta.

[55][56][57] Prior to the 2010 Census, Greenwich Township had been part of the 5th Congressional District, a change made by the New Jersey Redistricting Commission that took effect in January 2013, based on the results of the November 2012 general elections.

[58] For the 119th United States Congress, New Jersey's 7th congressional district is represented by Thomas Kean Jr. (R, Westfield).

[60] For the 2024-2025 session, the 23rd legislative district of the New Jersey Legislature is represented in the State Senate by Doug Steinhardt (R, Lopatcong Township) and in the General Assembly by John DiMaio (R, Hackettstown) and Erik Peterson (R, Franklin Township).

[65][66] Constitutional officers of Warren County are: Clerk Holly Mackey (R, Alpha; 2027),[67][68] Sheriff James McDonald Sr. (R, Phillipsburg; 2025)[69][70] and Surrogate Michael J. Doherty (R, Washington; 2025).

[74] Among the township's 2010 Census population, 61.4% (vs. 62.3% in Warren County) were registered to vote, including 91.6% of those ages 18 and over (vs. 81.5% countywide).

A small part of the Norfolk Southern Railway's Lehigh Line (formerly the mainline of the Lehigh Valley Railroad), runs through the southern part of Greenwich Township on its way to Phillipsburg, New Jersey.

[citation needed] People who were born in, residents of, or otherwise closely associated with Greenwich Township include: