[24] Before European settlement, the land was settled by the Lenape Native Americans, whose presence remains in the names of places and bodies of water in the township.

[25] Bethlehem was first mentioned in official records dating back to 1730, though details of its formation are uncertain.

[21] The Musconetcong River forms the township's northern border with Warren County.

Unincorporated communities, localities and place names located partially or completely within the township include Charlestown, Jugtown, Ludlow, Polktown, Swinesburg, Valley and West Portal.

[30][31][32] Residents and businesses in Bethlehem Township have mailing addresses to nearby towns including Bloomsbury, Clinton, Glen Gardner, Hampton, and even Asbury (which is located in neighboring Warren County), as "Bethlehem Township" itself is not a mailing address.

[33] Bethlehem Township falls under the "Northern New Jersey" climate zone.

According to the Office of the New Jersey State Climatologist at Rutgers University, the Northern climate zone covers about one-quarter of New Jersey and consists mainly of elevated highlands and valleys which are part of the Appalachian Uplands.

Surrounded by land, this region can be characterized as having a continental climate with minimal influence from the Atlantic Ocean, except when the winds contain an easterly component.

[36] Various animals are native to central-western New Jersey, including red fox (vulpes vulpes),[37] black bear, groundhogs, wild turkeys, deer, squirrels, chipmunks, a variety of birds, and a wide variety of insects and vegetation.

Black bears are the largest land mammals in New Jersey and are known to be most abundant in the northern-western regions of the state, including Bethlehem Township.

The 2010 United States census counted 3,979 people, 1,344 households, and 1,148 families in the township.

[49] As of the 2000 United States census[18] there were 3,820 people, 1,266 households, and 1,092 families residing in the township.

[47][48] Most common first ancestries reported in Bethlehem Township were German (25.2%), Italian (14.7%), Irish (14.4%), Polish (9.2%), English (7.6%), United States or American (6.1%), French (except Basque) (3.3%).

[50] The most common places of birth for the foreign-born residents were India (22%), Germany (18%), United Kingdom (12%), Austria (9%), Russia (7%), Poland (5%), Netherlands (4%).

[50] Covering more than 2,000 acres (810 ha), Spruce Run State Park and Reservoir, part of the New Jersey State Park system, is located near Bethlehem Township in close by Clinton Township.

[3][54][28][55][56][57][58] At a special meeting in July 2015, The Township Committee selected Jose Medeiros to fill the seat expiring in December 2017 that was vacated earlier that month following the resignation of John Graefe, who was moving out of the township.

[61][62][63] For the 119th United States Congress, New Jersey's 7th congressional district is represented by Thomas Kean Jr. (R, Westfield).

[65] 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).

[72][73] Constitutional officers elected on a countywide basis are Clerk Mary H. Melfi (R; Flemington, 2026),[74][75] Sheriff Fredrick W. Brown (R; Alexandria Township, 2025)[76][77] and Surrogate Heidi Rohrbach (R; Lebanon Township, 2028).

[99][100][101] Eighth grade students from all of Hunterdon County are eligible to apply to attend the high school programs offered by the Hunterdon County Vocational School District, a county-wide vocational school district that offers career and technical education at its campuses in Raritan Township and at programs sited at local high schools, with no tuition charged to students for attendance.