When Wilmington township was formed in 1846, it embraced considerably more territory than it now does. When Lawrence county was created in 1849, the north line of that county was so run as to cut Wilmington township in two, leaving in Mercer county only about a third of the original area.

The natural commercial center of the township is at New Wilmington. In March, 1858, a postoffice was established on the little stream in the northeast corner of the township, called Indian Run. Since 1902 the office has been discontinued.

A colony of settlers came to this vicinity in 1798 and established families, several of which have since been identified with this township. The colonists were John McCrum, James Hazlet, John Waugh, William Hughey, John Blair, Robert Weir, John Hughson. Hugh Means was an important settler of 1800, for about four years later he built the first grist mill. James Young was also one of the early settlers here.

Twentieth Century History of Mercer County, 1909, page 167