Bollinger County is a county located in the southeastern part of the U.S. state of Missouri. As of the 2020 census, the county's population was 10,567. The county seat, largest and only city, is Marble Hill. The largely rural county is supported by agriculture and construction. The county was officially organized in March 1851 from portions of Wayne, Cape Girardeau and Stoddard Counties, and named in honor of George Frederick Bollinger, an early settler.

Madison County is a county located in the Lead Belt region of the U.S. state of Missouri. As of the 2020 census, the population was 12,626. Its county seat and largest city is Fredericktown. The county was officially organized on December 14, 1818, and was named after President James Madison.