On April 1, 1889, Samukawa District (寒川郡), Shimotsuke was merged into Shimotsuga District. On January 10, 2006, the towns of Kokubunji and Ishibashi merged with the town of Minamikawachi, from Kawachi District, to form part of the new city of Shimotsuke. On March 29, 2010, the towns of Fujioka, Ōhira and Tsuga merged into the city of Tochigi.