Kyushu is the third largest island of Japan and most southwesterly of its four main islands. Its alternate ancient names include Kyūkoku, Chinzei, and Tsukushi-no-shima. The historical regional name is Saikaidō referred to Kyushu and its surrounding islands. In the 8th century Taihō Code reforms, Dazaifu was established as a special administrative term for the region. As of 2006, Kyushu has a population of 13,231,995 and covers 35,640 square kilometres (13,760 sq mi).