In the early 19th century, zinc deposits in the area began to be developed commercially.

For most of the century many small companies mined zinc and iron in the Franklin area.

Immigrants from Russia, Britain, Hungary and Poland joined the work force at the mine.

On March 18, 1913, the Borough of Franklin was incorporated from portions of Hardyston Township, based on the results of a referendum held on April 23, 1913.

[32] The 2010 United States census counted 5,045 people, 1,936 households, and 1,316 families in the borough.

[38] As of the 2000 United States census[17] there were 5,160 people, 1,898 households, and 1,324 families residing in the borough.

[8] The borough form of government used by Franklin is a "weak mayor / strong council" government in which council members act as the legislative body with the mayor presiding at meetings and voting only in the event of a tie.

The mayor can veto ordinances subject to an override by a two-thirds majority vote of the council.

[40][41] As of 2024[update], the mayor of Franklin Borough is Republican John M. Sowden IV, whose term of office ends December 31, 2027.

Members of the Borough Council are Concetto Formica (R, 2025), Rachel Heath (R, 2024), Joseph Limon (R, 2026), John E. Postas (R, 2026), Stephen M. Skellenger (R, 2025) and Gilbert J. Snyder (R, 2024).

[47][48][49] For the 119th United States Congress, New Jersey's 5th congressional district is represented by Josh Gottheimer (D, Wyckoff).

[52] For the 2024-2025 session, the 24th legislative district of the New Jersey Legislature is represented in the State Senate by Parker Space (R, Wantage Township) and in the General Assembly by Dawn Fantasia (R, Franklin) and Mike Inganamort (R, Chester Township).

At an annual reorganization meeting held in the beginning of January, the board selects a Commissioner Director and Deputy Director from among its members, with day-to-day supervision of the operation of the county delegated to a County Administrator.

[64] Among the borough's 2010 Census population, 60.9% (vs. 65.8% in Sussex County) were registered to vote, including 78.2% of those ages 18 and over (vs. 86.5% countywide).

[80] For ninth through twelfth grades, public school students attend Wallkill Valley Regional High School which also serves students from Hamburg Borough, Hardyston Township and Ogdensburg Borough, and is part of the Wallkill Valley Regional High School District.

[87] The county provides Skylands Ride bus service operating between Sussex and Newton.