Ganghwa County is a county in the city of Incheon, South Korea. The county is composed of Ganghwa Island, and the minor islands aroun…Ganghwa County is a county in the city of Incheon, South Korea. The county is composed of Ganghwa Island, and the minor islands around it. Ganghwa County contains some of the most important historical sites in Korea. These sites cover the prehistoric old and new stone ages, as well as the bronze and iron ages. Additionally there are numerous historic sites.