 New Jersey's first counties were created as administrative districts within each province, with East Jersey split in 1675 into Bergen, Essex, Middlesex and Monmouth counties, while West Jersey's initial counties of Burlington and Salem date to 1681.The most recent county created in New Jersey is Union County, created in 1857 and named after the union of the United States when the Civil War was imminent.New Jersey's county names derive from several sources, though most of its counties are named after place names in England and prominent leaders in the colonial and revolutionary periods.