Alcohol Treatment Center in Ewing, NJ.

The earliest inhabitants of present-day Ewing Township in the historic era were Lenni Lenape Native Americans, who lived along the banks of the Delaware River. Their pre-colonial subsistence activities in the area included hunting, fishing, pottery-making, and simple farming. European settlers, mostly from the British Isles, began to colonize the area in 1699. One of the earliest European settlers was William Green, and his 1717 farmhouse still stands on the campus of The College of New Jersey.

The area that is now Ewing Township was part of Hopewell Township in what was a very large Burlington County at the beginning of the 18th century. In 1714 Hopewell was removed from Burlington County and added to Hunterdon County. By 1719, the area which was to become Ewing Township had been removed from Hopewell Township and added to the newly created Trenton Township. Portions of Trenton Township were incorporated as Ewing Township by an act of the New Jersey Legislature on February 22, 1834, posthumously honoring Charles Ewing for his work as Chief Justice of the New Jersey Supreme Court. The township became part of the newly created Mercer County on February 22, 1838. After incorporation, Ewing Township received additional territory taken from Lawrence Township and the city of Trenton in 1858. In 1894 the city of Trenton took back some of that territory, annexing more in 1900.

When Ewing Township was incorporated in the 19th century, it was primarily farmland with a handful of scattered hamlets, including Carleton (now known as Ewing), Cross Keys (now known as Ewingville), Birmingham (now known as West Trenton) and Greensburg (now known as Wilburtha). Since the beginning of the 20th century, the township has developed as a suburb of Trenton. The sections near the city border are distinctly urban, but most of the township is suburban residential development. The main commercial district extends along North Olden Avenue Extension (County Route 622), originally constructed to connect north Trenton residences with the now-closed General Motors Inland Fisher Guide Plant. Ewing Township today is the location of The College of New Jersey, the Community Blood Council of New Jersey, New Jersey State Police headquarters, the Jones Farm State Correction Institute, the Trenton Psychiatric Hospital, the New Jersey Department of Transportation headquarters, the Maria H. Katzenbach School for the Deaf and Trenton-Mercer Airport.