Portions of the township were taken to form North Plainfield (June 9, 1885) and Watchung (March 23, 1926).

Thirteen years later, in 1885, the Borough of North Plainfield was created from a section of the subdivided land.

It then continues southwestward and flows into the Raritan River at Bound Brook, which provides access to the New York City area and the Atlantic Ocean.

[24] Also contained within the township is Washington Rock State Park, which commemorates the spot where George Washington and Marquis de Lafayette watched the movement of the British soldiers during the American Revolutionary War, mainly the months of May and June 1777.

[2][3] The township is in the Raritan Valley, a line of places in central New Jersey.

Green Brook lies in the northern division of Raritan Valley along with the borough of North Plainfield.

[26] Unincorporated communities, localities and place names located partially or completely within the township include Seeley Mills and Washington Rock.

[28][29][30] The 2010 United States census counted 7,203 people, 2,375 households, and 1,945 families in the township.

[41] As of the 2000 United States census[16] there were 5,654 people, 1,893 households, and 1,508 families residing in the township.

15.9% of all households were made up of individuals, and 6.2% had someone living alone who was 65 years of age or older.

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

[52] For the 2024-2025 session, the 21st legislative district of the New Jersey Legislature is represented in the State Senate by Jon Bramnick (R, Westfield) and in the General Assembly by Michele Matsikoudis (R, New Providence) and Nancy Munoz (R, Summit).

[53] Somerset County is governed by a five-member Board of County Commissioners, whose members are elected at-large to three-year terms of office on a staggered basis, with one or two seats coming up for election each year.

[70] Among the township's 2010 Census population, 63.1% (vs. 60.4% in Somerset County) were registered to vote, including 85.7% of those ages 18 and over (vs. 80.4% countywide).

Students from Green Brook and from the neighboring communities of Watchung, Warren Township (in Somerset County), and Long Hill Township (in Morris County) attend the school.

[90] U.S. Route 22 is the most prominent highway directly serving Green Brook.

The Green Brook Recreation Committee is a volunteer organization that provides programs and event for all residents.

People who were born in, residents of, or otherwise closely associated with Green Brook Township include: