[11] The most populous place in Salem County is Pennsville Township with 12,684 residents as of the 2020 Census.

[6] Lower Alloways Creek Township covers 72.46 square miles (187.7 km2), the largest total area of any municipality.

[13] The county derives its name from the Hebrew word shalom, which means "peace", chosen by early Quaker settlers to mark the serenity of the area.

[2][14] European settlement began with English colonists in the seventeenth century, who were settling both sides of the Delaware River.

[15] The courthouse was built in 1735 during the reign of King George II using locally manufactured bricks.

Four men were convicted and sentenced to death for treason; however, they were pardoned by Governor William Livingston and exiled from New Jersey.

The courthouse is also the site of the legend of Colonel Robert Gibbon Johnson's proving the edibility of the tomato.

In 1820, Colonel Johnson, according to legend, stood upon the courthouse steps and ate tomatoes in front of a large crowd assembled to watch him do so.

[18] Salem County is notable for its distinctive Quaker-inspired architecture and masonry styles of the 18th century.

In the early 20th century, its towns received numerous immigrants from eastern and southern Europe, who markedly added to the population.

In the period following World War II, the county's population increased due to suburban development.

[29][30] The 2010 United States census counted 66,083 people, 25,290 households, and 17,551 families in the county.

[11] Salem County is governed by a five-member Board of 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.

The appointed position professional county administrator was abolished by a unanimous vote of the commissioners in January 2014.

[32] In the 2016 general election, Salem County voters approved a binding referendum to cut the number of Commissioner from seven to five as well as a non-binding referendum to cut Commissioner salaries by 20%; both initiatives, which had been placed on the ballot as the result of grassroots campaigns opposed to a proposed outsourcing deal, passed by a 3–1 margin.

[33] In the wake of the referendum results, Director Julie Acton resigned in December 2016 and was replaced by Scott Griscom.

[34] In April 2017, the New Jersey Supreme Court ruled that the reduction in seats will be accomplished through attrition, with the seats expiring at the end of 2017 (held by Commissioners Cross, Painter, and Vanderslice) being eliminated; in the November 2017 general election there will be one new three-year seat up for a vote as well as a two-year unexpired term, so that on January 1, 2018, there will be a five-member board.

[35] As of 2025[update], Salem County's Commissioners (with terms for director and deputy director ending every December 31) are:[36][37][38][39][40] Pursuant to Article VII Section II of the New Jersey State Constitution, each county in New Jersey is required to have three elected administrative officials known as "constitutional officers."

[60][61] The Bureau of Economic Analysis calculated that the county's gross domestic product was $5.2 billion in 2021, which was ranked 18th in the state and was a 3.9% increase from the prior year.

[79] The 15 municipalities in Salem County (with 2010 Census data for population, housing units and area in square miles) are:[80] Other, unincorporated communities in the county are listed next to their parent municipality.

Some of these areas are census-designated places (CDPs) that have been created by the United States Census Bureau for enumeration purposes within a Township.