According to the 2010 Census, the county had a total area of 677.62 square miles (1,755.0 km2), including 483.70 square miles (1,252.8 km2) of land (71.4%) and 193.92 square miles (502.3 km2) of water (28.6%).
Cumberland is a low-lying, generally featureless coastal county, with many salt marshes near the Delaware Bay. The highest elevation is at one of 12 areas in Upper Deerfield Township that stand approximately 140 feet (43 m) above sea level; the lowest elevation is sea level.
The 51,931 households accounted 31.4% with children under the age of 18 living with them; 45.2% were married couples living together; 18.6% had a female householder with no husband present, and 29.6% were non-families. 24% of all households were made up of individuals, and 10.8% had someone living alone who was 65 years of age or older. The average household size was 2.79 and the average family size was 3.26.
In the county, the population age was spread out with 24% under the age of 18, 9.5% from 18 to 24, 28.5% from 25 to 44, 25.3% from 45 to 64, and 12.6% who were 65 years of age or older. The median age was 36.5 years. For every 100 females, the population had 106.2 males. For every 100 females ages 18 and older there were 106.9 males.
There were 49,143 households out of which 34.10% had children under the age of 18 living with them, 48.70% were married couples living together, 17.30% had a female householder with no husband present, and 28.40% were non-families. 23.60% of all households were made up of individuals and 11.10% had someone living alone who was 65 years of age or older. The average household size was 2.73 and the average family size was 3.19.
In the county, the population was spread out with 25.40% under the age of 18, 8.50% from 18 to 24, 31.20% from 25 to 44, 21.90% from 45 to 64, and 13.00% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 104.20 males. For every 100 females age 18 and over, there were 103.50 males.
The median income for a household in the county was $39,150, and the median income for a family was $45,403. Males had a median income of $35,387 versus $25,393 for females. The per capita income for the county was $17,376. About 11.3% of families and 15.0% of the population were below the poverty line, including 20.1% of those under age 18 and 12.9% of those age 65 or over.
Cumberland County is governed by a Board of Chosen Freeholders consisting of seven members. Each Freeholder is assigned responsibility for one of the County's departments. These individuals are elected at large by the citizens of Cumberland County in partisan elections and serve staggered three-year terms in office, with either two or three seats coming up for election each year in a three-year cycle. In 2016, freeholders were paid $15,000 and the freeholder director was paid an annual salary of $16,000.
As of 2018[update], members of the Cumberland County Board of Chosen Freeholders (with party affiliation, residence and term-end year listed in parentheses) are:
Freeholder Director Joseph Derella Jr. (D, Millville, term as freeholder and as freeholder director ends December 31, 2018)
Deputy Freeholder Director Darlene R. Barber (D, Upper Deerfield Township, term as freeholder ends 2019, term as deputy freeholder director ends 2018)
Then-Freeholder Director Bill Whelan, whose term was to run to December 2014, announced in July 2013 that he was resigning from office. Later that month, Joe Derella was chosen to replace Whelan as director, while the vacant seat was filled by Vineland resident Carlos Mercado.
Freeholder Louis N. Magazzu, whose term was to expire in 2012, announced his resignation in August 2011.
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." These officers are the County Clerk and County Surrogate (both elected for five-year terms of office) and the County Sheriff (elected for a three-year term). Cape May's Constitutional offers are:
As of 2010[update], the county had a total of 1,271.74 miles (2,046.67 km) of roadways, of which 643.65 miles (1,035.85 km) were maintained by the local municipality, 539.14 miles (867.66 km) by Cumberland County and 88.95 miles (143.15 km) by the New Jersey Department of Transportation.
In recent years, average temperatures in the county seat of Bridgeton have ranged from a low of 25 °F (−4 °C) in January to a high of 87 °F (31 °C) in July, although a record low of −13 °F (−25 °C) was recorded in January 1985 and a record high of 101 °F (38 °C) was recorded in July 1966. Average monthly precipitation ranged from 2.94 inches (75 mm) in February to 4.30 inches (109 mm) in March. Cumberland has a humid subtropical climate (Cfa).
^Baehr, Judy. "Cumberland – A County Born of Hope, Optimism"Archived 2007-12-16 at the Wayback Machine, Cumberland County, New Jersey. Accessed December 13, 2007. "The county was named for William Augustus, the second son of King George II. As the Duke of Cumberland in 1746, he had defeated the Stuart Pretender, Charles Edward (Bonnie Prince Charlie), at the battle of Culloden and established the House of Hanover on the British throne."
^About Cumberland County Government, Cumberland County, New Jersey. Accessed June 7, 2018. "By law, Cumberland County is allowed 7 freeholders, who serve staggered, overlapping three year terms. Two are elected in two successive years, three in the third year, elected from the county at-large. A Director of the Board is selected by his colleagues for a one year term."
^Smith, Joseph P. "Sexting scandal ends S.J. freeholder's career", Courier Post, August 3, 2011. Accessed August 3, 2011. "Louis N. Magazzu resigned from the board of freeholders Tuesday after a decade at the top of Democratic politics. His departure came after an embarrassing sexting scandal made the jump from a private website and local gossip circles into print and television media."
^Jennifer Webb-McRae, Cumberland County Prosecutor's Office. Accessed October 25, 2017. "In January of 2010, Jennifer was nominated by Governor Jon S. Corzine to be the first African American, first female Prosecutor of Cumberland County.... In November of 2016, Governor Chris Christie nominated Prosecutor Webb-McRae for a second five year term as Cumberland County Prosecutor. In January of 2017, Prosecutor Webb-McRae was sworn in becoming the first full-time Prosecutor in Cumberland County to serve a second term."