According to the United States Census Bureau, the township had a total area of 20.687 square miles (53.580 km2), including 19.956 square miles (51.686 km2) of land and 0.731 square miles (1.894 km2) of water (3.53%).
Unincorporated communities, localities and place names located partially or completely within the township include Brighton, County Road Camp, Davis Pond, Drakes Pond, Garders Lake, Iliffs Lake, Lake Aeroflex, Lake Iliff, Lake Lenape, Long Pond, Mulford, New Waywayanda Lake, Pinkneyville, Redings Pond, Springdale, Stickle Pond, Sussex Mills, Whitehall and Whites Pond.
The 2010 United States Census counted 6,319 people, 2,070 households, and 1,590 families residing in the township. The population density was 316.6 per square mile (122.2/km2). The township contained 2,181 housing units at an average density of 109.3 per square mile (42.2/km2). The racial makeup of the township was 91.64% (5,791) White, 3.37% (213) Black or African American, 0.17% (11) Native American, 2.60% (164) Asian, 0.00% (0) Pacific Islander, 0.73% (46) from other races, and 1.49% (94) from two or more races. Hispanics or Latinos of any race were 5.14% (325) of the population.
Out of a total of 2,070 households, 34.9% had children under the age of 18 living with them, 64.8% were married couples living together, 7.9% had a female householder with no husband present, and 23.2% were non-families. 19.2% of all households were made up of individuals, and 6.0% had someone living alone who was 65 years of age or older. The average household size was 2.70 and the average family size was 3.10.
In the township, 22.1% of the population were under the age of 18, 5.5% from 18 to 24, 22.2% from 25 to 44, 34.2% from 45 to 64, and 16.0% who were 65 years of age or older. The median age was 45.1 years. For every 100 females the census counted 99.8 males, but for 100 females at least 18 years old, it was 95.6 males.
The Census Bureau's 2006-2010 American Community Survey showed that (in 2010 inflation-adjusted dollars) median household income was $95,313 (with a margin of error of +/- $10,064) and the median family income was $105,554 (+/- $13,995). Males had a median income of $72,066 (+/- $10,198) versus $47,750 (+/- $8,020) for females. The per capita income for the borough was $38,284 (+/- $4,082). About 2.3% of families and 2.9% of the population were below the poverty line, including 1.0% of those under age 18 and 0.0% of those age 65 or over.
As of the 2000 United States Census there were 6,033 people, 1,889 households, and 1,499 families residing in the township. The population density was 298.9 people per square mile (115.4/km2). There were 1,968 housing units at an average density of 97.5 per square mile (37.7/km2). The racial makeup of the township was 94.45% White, 1.86% African American, 0.08% Native American, 2.30% Asian, 0.03% Pacific Islander, 0.60% from other races, and 0.68% from two or more races. Hispanic or Latino of any race were 2.25% of the population.
There were 1,889 households out of which 39.8% had children under the age of 18 living with them, 67.9% were married couples living together, 8.0% had a female householder with no husband present, and 20.6% were non-families. 16.1% of all households were made up of individuals and 5.0% had someone living alone who was 65 years of age or older. The average household size was 2.80 and the average family size was 3.16.
In the township the population was spread out with 25.0% under the age of 18, 4.6% from 18 to 24, 28.9% from 25 to 44, 25.7% from 45 to 64, and 15.7% who were 65 years of age or older. The median age was 40 years. For every 100 females there were 91.9 males. For every 100 females age 18 and over, there were 87.2 males.
The median income for a household in the township was $75,748, and the median income for a family was $78,439. Males had a median income of $57,098 versus $36,268 for females. The per capita income for the township was $29,180. About 1.3% of families and 3.5% of the population were below the poverty line, including 1.9% of those under age 18 and 5.3% of those age 65 or over.
Andover Township is governed under the Township form of government by a five-member Township Committee. The five-member Township Committee is elected directly by the voters at-large in partisan elections to serve three-year terms of office on a staggered basis, with either one or two seats coming up for election each year as part of the November general election in a three-year cycle. At an annual reorganization held in January, the council selects a mayor and a deputy mayor from among its members.
As of 2016, members of the Andover Township Committee are Mayor Dolores Blackburn (R, term as mayor ends December 31, 2017; term on township committee ends 2016), Deputy Mayor John Burke (R, term on committee ends 2017; term as deputy mayor ends 2016), Ellsworth E. Bensley Jr. (R, 2018), Janis L. McGovern (R, 2018) and Thomas D. Walsh Jr. (R, 2016).
Andover Township is located in the 5th Congressional district and is part of New Jersey's 24th state legislative district.
New Jersey's Fifth Congressional District is represented by Josh Gottheimer (D, Wyckoff). New Jersey is represented in the United States Senate by Cory Booker (D, Newark, term ends 2021) and Bob Menendez (D, Paramus, 2019).
For the 2016–2017 session (Senate, General Assembly), the 24th Legislative District of the New Jersey Legislature is represented in the State Senate by Steve Oroho (R, Franklin) and in the General Assembly by Parker Space (R, Wantage Township) and Gail Phoebus (R, Andover Township). The Governor of New Jersey is Chris Christie (R, Mendham Township). The Lieutenant Governor of New Jersey is Kim Guadagno (R, Monmouth Beach).
Sussex County is governed by a Board of Chosen Freeholders whose five members are elected at-large in partisan elections on a staggered basis, with either one or two seats coming up for election each year. At an annual reorganization meeting held in the beginning of January, the board selects a Freeholder Director and Deputy Director from among its members, with day-to-day supervision of the operation of the county delegated to a County Administrator. As of 2014, Sussex County's Freeholders are Freeholder Director Richard Vohden (R, Green Township, 2016), Deputy Director Dennis J. Mudrick (R, Sparta Township, 2015), Phillip R. Crabb (R, Franklin, 2014), George Graham (R, Stanhope, 2016) and Gail Phoebus (R, Andover Township, 2015). Graham was chosen in April 2013 to fill the seat vacated by Parker Space, who had been chosen to fill a vacancy in the New Jersey General Assembly. Constitutional officers elected on a countywide basis are County Clerk Jeff Parrott (R, 2016), Sheriff Michael F. Strada (R, 2016) and Surrogate Gary R. Chiusano (R, filling the vacancy after the resignation of Nancy Fitzgibbons). The County Administrator is John Eskilson.
As of March 23, 2011, there were a total of 3,979 registered voters in Andover Township, of which 606 (15.2% vs. 16.5% countywide) were registered as Democrats, 1,813 (45.6% vs. 39.3%) were registered as Republicans and 1,552 (39.0% vs. 44.1%) were registered as Unaffiliated. There were 8 voters registered to other parties. Among the township's 2010 Census population, 63.0% (vs. 65.8% in Sussex County) were registered to vote, including 80.8% of those ages 18 and over (vs. 86.5% countywide).
In the 2012 presidential election, Republican Mitt Romney received 1,703 votes (60.7% vs. 59.4% countywide), ahead of Democrat Barack Obama with 1,034 votes (36.8% vs. 38.2%) and other candidates with 62 votes (2.2% vs. 2.1%), among the 2,807 ballots cast by the township's 4,074 registered voters, for a turnout of 68.9% (vs. 68.3% in Sussex County). In the 2008 presidential election, Republican John McCain received 1,772 votes (59.0% vs. 59.2% countywide), ahead of Democrat Barack Obama with 1,173 votes (39.1% vs. 38.7%) and other candidates with 37 votes (1.2% vs. 1.5%), among the 3,002 ballots cast by the township's 3,948 registered voters, for a turnout of 76.0% (vs. 76.9% in Sussex County). In the 2004 presidential election, Republican George W. Bush received 1,799 votes (64.0% vs. 63.9% countywide), ahead of Democrat John Kerry with 966 votes (34.4% vs. 34.4%) and other candidates with 30 votes (1.1% vs. 1.3%), among the 2,811 ballots cast by the township's 3,566 registered voters, for a turnout of 78.8% (vs. 77.7% in the whole county).
In the 2013 gubernatorial election, Republican Chris Christie received 71.2% of the vote (1,212 cast), ahead of Democrat Barbara Buono with 25.1% (427 votes), and other candidates with 3.8% (64 votes), among the 1,718 ballots cast by the township's 4,121 registered voters (15 ballots were spoiled), for a turnout of 41.7%. In the 2009 gubernatorial election, Republican Chris Christie received 1,271 votes (64.4% vs. 63.3% countywide), ahead of Democrat Jon Corzine with 482 votes (24.4% vs. 25.7%), Independent Chris Daggett with 195 votes (9.9% vs. 9.1%) and other candidates with 22 votes (1.1% vs. 1.3%), among the 1,974 ballots cast by the township's 3,882 registered voters, yielding a 50.9% turnout (vs. 52.3% in the county).
Public school students in pre-kindergarten through eighth grade attend the Andover Regional School District, together with students from Andover Borough. As of the 2014-15 school year, the district and its two schools had an enrollment of 852 students and 55.3 classroom teachers (on an FTE basis), for a student–teacher ratio of 15.4:1. Schools in the district (with 2014-15 enrollment data from the National Center for Education Statistics) are Florence M. Burd Elementary School (Grades PreK-4, 279 students) and Long Pond Middle School (Grades 5-8, 280 students).
Public school students in ninth through twelfth grades attend Newton High School in Newton, together with students from Andover Township and Green Township, as part of a sending/receiving relationship with the Newton Public School District. As of the 2014-15 school year, the high school had an enrollment of 773 students and 66.5 classroom teachers (on an FTE basis), for a student–teacher ratio of 11.6:1.
As of May 2010, the township had a total of 73.42 miles (118.16 km) of roadways, of which 49.13 miles (79.07 km) were maintained by the municipality, 20.79 miles (33.46 km) by Sussex County and 3.50 miles (5.63 km) by the New Jersey Department of Transportation.
People who were born in, residents of, or otherwise closely associated with Andover Township include:Gail Phoebus (born 1950), member of the New Jersey General Assembly, who previously served on the Andover Township Committee and as a Sussex County Freeholder.