 Nikkō was incorporated as a town in 1889 (part of Kamitsuga District).It was upgraded to city status in 1954 after merging with the neighboring village of Okorogawa.On March 20, 2006, Nikkō absorbed the old city of Imaichi, the town of Ashio (from Kamitsuga District), the town of Fujihara, and the village of Kuriyama (both from Shioya District), to create what is officially the new and expanded city of Nikkō.