It had been previously known as East Fenwick Township, which was mentioned on September 3, 1679, though the details of its incorporation are unknown.

[19] The township's name derives from the Lenape deity, variously spelled as Maneto or Manito.

[23][24] Among the oldest buildings are Barrett's Plantation House and the Salem County Insane Asylum.

[26][27] Unincorporated communities, localities and place names located partially or completely within the township include Acton, Claysville,[28] Halltown, Marshalltown, Pointers, Portertown, Slapes Corner, Welchtown and Welchville.

[29] The 2010 United States census counted 1,806 people, 540 households, and 392 families in the township.

[41] As of the 2000 United States census[13] there were 1,559 people, 539 households, and 409 families residing in the township.

In 2010, the company undertook an extensive cleanup of contaminated soil on the plant site.

[51][52][53] For the 119th United States Congress, New Jersey's 2nd congressional district is represented by Jeff Van Drew (R, Dennis Township).

[55] For the 2024-2025 session, the 3rd legislative district of the New Jersey Legislature is represented in the State Senate by John Burzichelli (D, Paulsboro) and in the General Assembly by David Bailey (D, Woodstown) and Heather Simmons (D, Glassboro).

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

Cross (R, Pennsville Township, 2029),[59][60] Sheriff Charles M. Miller (R, Salem, 2027)[61][62] and Surrogate Nicki A. Burke (D, Woodstown, 2025).

[65] Among the township's 2010 Census population, 56.1% (vs. 64.6% in Salem County) were registered to vote, including 68.7% of those ages 18 and over (vs. 84.4% countywide).

[88] New Jersey Route 45 (Salem-Woodstown Road) is the main highway serving Mannington Township.

[95][96] Once also providing passenger service, the 18.6 miles (29.9 km) southern portion of the freight rail Salem Branch operated under contract by Southern Railroad of New Jersey runs through Mannington, with Mannington Mills being one of the short line's major customers.

[97][98] Salem Medical Center is a 126-bed hospital that was founded in 1919 and moved to Mannington Township in 1951.

In 2017, New Jersey approved a plan to sell it to Prime Healthcare Foundation for $15 million.