Wilmington is the county seat of Clinton County, Ohio. Many of the town's early residents were from North Carolina, and they named their new community, which was established in 1810, after Wilmington, North Carolina. The community grew quickly, attaining 1,500 residents by 1840. In 1846, the community had five churches, one high school, one newspaper, and nineteen retail stores.
By 1880, Wilmington had almost doubled in size, achieving a population of 2,745 residents. In 1886, two railroads passed through the community, and the town consisted of three newspaper offices, nine churches, and two banks. Most manufacturing businesses either processed farm products or manufactured farming implements for local use. Several locals also found employment at Wilmington College. The Society of Friends established this college in 1870.
During the twentieth century, Wilmington experienced continued growth. In 2000, the town had a population of 11,921 people in 2000. It is also the home to a National Weather Service station. Residents claim that the first banana split was created in their community. This event occurred at Hazard's Drug Store in 1907.