Long before European settlement, the land that is now Franklin Township was inhabited by the Lenape Native Americans, who lived along the Raritan and Millstone rivers, utilizing the fertile floodplains for agriculture and the waterways for transportation.
European settlement began in the late 17th and early 18th centuries, primarily by Dutch and English farmers moving westward from earlier coastal settlements. During the American Revolutionary War, the township was a site of strategic importance. George Washington and his Continental Army utilized the area's roads and resources, with several historic homes in the township famously hosting generals and troops.
Franklin Township was officially incorporated as one of New Jersey's original 104 townships on February 21, 1798. It was named in honor of Benjamin Franklin. In the 1830s, the construction of the Delaware and Raritan Canal revolutionized local commerce, allowing coal and agricultural products to be transported between Philadelphia and New York.
Throughout the 20th century, Franklin evolved from a predominantly agricultural community into a thriving suburb. Post-World War II suburbanization brought new housing developments and the expansion of the Route 27 corridor. Despite this rapid growth, the township has made aggressive and successful efforts in the 21st century to preserve thousands of acres of historic farmland and open space.