[19] Most of the township lies on the Hunterdon Plateau with only the eastern section along the South Branch Raritan River being on the lower part of the Newark Basin.

Long populated by the Lenape (Delaware) Native Americans, the first European settlement of present-day Franklin was around 1700, when it became a Quaker community of settlers who came from Burlington County.

The most reliable records that are available about the early days of the Township are found in the minutes of the Friends' Meeting in Quakertown.

[23] The rich soil made the township a center of agriculture for hundreds of years.

While Franklin Township had long hosted a major dairy farming industry, in modern times, the primary crops have been corn, hay and soybeans.

[1][2] Unincorporated communities, localities and place names located partially or completely within the township include Allens Corner, Alvater Corner,[citation needed] Cherryville (previously known as Dogtown), Grandin,[citation needed] Kingtown, Lansdowne, Littletown, Oak Grove, Pittstown, Quakertown (previously known as Fairview), Sidney and Sunnyside.

[21] The Capoolong Creek, which runs through Pittstown, was an attraction to early settlers and they soon established three of the oldest churches in present-day Hunterdon: Thomas Episcopal, established in 1723, Bethlehem Presbyterian, organized in 1730 and the Quaker Church in 1733.

[26][27][28] The 2010 United States census counted 3,195 people, 1,137 households, and 908 families in the township.

[39] As of the 2000 United States census[14] there were 2,990 people, 1,091 households, and 890 families residing in the township.

[3][43][20][44][45][46][47] In January 2019, the Township Committee selected Sebastian Donaruma from a list of three candidates nominated by the Republic municipal committee to fill the seat expiring in December 2019 that was vacated in December 2018 by Susan Soloway before she was sworn into the Hunterdon County Board of Chosen Freeholders.

[50][51][52] Prior to the 2010 Census, Franklin Township had been part of the 12th 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.

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

[55] 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).

[62][63] Constitutional officers elected on a countywide basis are Clerk Mary H. Melfi (R; Flemington, 2026),[64][65] Sheriff Fredrick W. Brown (R; Alexandria Township, 2025)[66][67] and Surrogate Heidi Rohrbach (R; Lebanon Township, 2028).

[84] The school is part of the North Hunterdon-Voorhees Regional High School District, which also includes students from Califon, Glen Gardner, Hampton, High Bridge, Lebanon Township and Tewksbury Township, who attend Voorhees High School in Lebanon Township.

[95] People who were born in, residents of, or otherwise closely associated with Franklin Township include: