John Ancrum was born in Scotland in about 1724. A longtime resident of Wilmington, Ancrum was a local justice of the peace and held a seat on the freeholders court, which heard cases involving enslaved people. During the American Revolution, Ancrum was a member of the Wilmington Committee of Safety. In 1777 he became the judge of admiralty for the port of Wilmington. He died sometime before October 1779.