Ewing Township was incorporated as a township by an Act of the New Jersey Legislature on February 22, 1834, from portions of Trenton Township, while the area was still part of Hunterdon County. It became part of the newly-created Mercer County on February 22, 1838.
Although Ewing Township was officially established in 1834, the history of the region ranges back thousands of years. The earliest inhabitants of the land area today known as Ewing Township were the Lenni Lenape Native Americans. These migratory people ranged throughout New Jersey along the banks of the Delaware River, and the Township's many creeks provided rich natural resources for hunting, fishing, pottery-making, and simple farming.
When the region was first settled by European colonists around 1699, it was part of Hopewell Township, and continued under that name until the City of Trenton was established in 1719. From 1719 until 1834, the area was named Trenton Township. On February 22, 1834, the name was changed from Trenton Township to Ewing Township in honor of Charles Ewing, who was posthumously honored for his work as Chief Justice of the New Jersey Supreme Court from 1824-1832.
As of the census of 2000, there were 35,707 people, 12,551 households, and 8,208 families residing in the township. The population density was 2,328.6 people per square mile (899.3/km). There were 12,924 housing units at an average density of 842.8/sq mi (325.5/km). The racial makeup of the township was 69.02% White, 24.82% African American, 0.15% Native American, 2.27% Asian, 0.06% Pacific Islander, 1.83% from other races, and 1.84% from two or more races. Hispanic or Latino of any race were 4.44% of the population.
There were 12,551 households out of which 25.3% had children under the age of 18 living with them, 49.7% were married couples living together, 12.2% had a female householder with no husband present, and 34.6% were non-families. 27.7% of all households were made up of individuals and 12.1% had someone living alone who was 65 years of age or older. The average household size was 2.45 and the average family size was 3.00.
In the township the population was spread out with 18.0% under the age of 18, 17.3% from 18 to 24, 26.8% from 25 to 44, 22.1% from 45 to 64, and 15.8% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 93.0 males. For every 100 females age 18 and over, there were 90.0 males.
The median income for a household in the township was $57,274, and the median income for a family was $67,618 (these figures had risen to $68,399 and $81,714 respectively as of a 2007 estimate). Males had a median income of $44,531 versus $35,844 for females. The per capita income for the township was $24,268. About 3.3% of families and 6.4% of the population were below the poverty line, including 5.4% of those under age 18 and 7.1% of those age 65 or over.
Ewing Township is traversed by multiple main roadways, as well as by a passenger rail line and is the location of an airport.
Route 29 (Daniel Bray Highway and River Road) extends north-south along the western edge of the township, along the Delaware River. The southern section, Daniel Bray Highway, is a 55 mph (90 km/h), divided 4-lane facility with at-grade intersections and traffic lights, and was constructed in the 1950s. The northern section, River Road, is a 45 mph (70 km/h), undivided 2-lane facility whose construction as a state highway dates from the 1930s. NJ 29 connects southwards to Trenton, and northwards to Lambertville and Frenchtown.
Route 31 (Pennington Road) extends north-south towards the eastern side of the township. It is a 35-45 mph (60–70 km/h), undivided 4-lane facility whose construction as a state highway also dates to the 1930s. It once also carried a trolley line, but it has long since been removed. It was once proposed to be bypassed by a freeway, but this plan has since been cancelled. NJ 31 also connects south to Trenton, and connects north to Pennington, Flemington, and Clinton.
U.S. Route 206 (Princeton Avenue) skirts the southeastern section of the township. It is a 25 mph (40 km/h), undivided 4-lane facility. Although part of US 206, it was not constructed and is not maintained by the state. US 206 also connects south to Trenton, and connects north to Princeton and Somerville.
Interstate 95 (the Scudder Falls Freeway and Bridge) crosses the northwestern section of the township. It is a 55-65 mph (90-100 km/h), 4-6 lane divided freeway facility. It was constructed as a 4-lane facility in the 1960s, and widened to 6 lanes in the 1990s, with the exception of the Scudder Falls Bridge over the Delaware River. It connects south with Philadelphia, Pennsylvania and connects north to U.S. 1, where this branch of Interstate 95 ends. It becomes Interstate 295. From there, travelers use U.S. 1 or Interstate 195 and the New Jersey Turnpike to reach the next major destination northwards, New York City. The Ewing portion of Interstate 95 will eventually be redesignated as "Interstate 195 Extension" when a direct interchange between Interstate 95 in Pennsylvania and the Pennsylvania Turnpike is completed, re-routing Interstate 95 onto the New Jersey Turnpike at Exit 6 (in Mansfield Township).
Ewing Township also boasts a commuter rail facility, West Trenton Station, at the terminus of SEPTA's R3 Regional Rail line. This facility mainly serves commuter traffic to and from Philadelphia, Pennsylvania.
Ewing Township is also the site of the Trenton-Mercer Airport (TTN). This facility is the site of limited commercial flights to various east coast locations, as well as a substantial public recreational airport.
Ewing Township is also traversed by the Delaware and Raritan Canal near the Delaware River. Originally important to commerce and trade, the advent of railroads caused the canal's commercial demise. The strip of land along the canal is currently part of the Delaware and Raritan Canal State Park, which comprises a section of the East Coast Greenway, an "urban" Appalachian Trail, aiming to connect all the major cities of the East Coast along a 3,000-mile (4,800 km) continuous off-road path from Calais, Maine to Key West, Florida.