Darby Township is one of the fourteen townships of Union County, Ohio, United States. The 2000 census found 1,934 people in the township, 1,634 of whom lived in the unincorporated portions of the township.GeographyLocated in the southern part of the county, it borders the following townships: Paris Township - northMillcreek Township - northeastJerome Township - eastDarby Township, Madison County - southPike Township, Madison County - southwestUnion Township - west Several populated places are located in Darby Township: A small part of the city of Marysville, the county seat of Union County, in the northThe village of Unionville Center in the southThe unincorporated community of Bridgeport, in the far westThe unincorporated community of Chuckery, in the far southwest