On February 28, 2005 - the towns of Kuzu and Tanuma from Aso District merged with the old city of Sano to form the new city of Sano. Aso District was dissolved as a result of this merger.
On March 28, 2005 - the towns of Kitsuregawa and Ujiie merged to form the city of Sakura.
On March 20, 2006 - the city of Imaichi, the town of Ashio from Kamitsuga District, the town of Fujihara and the village of Kuriyama (both from Shioya District) merged with the old city of Nikkō to form the new city of Nikkō. With this merger, there are no more villages left within Tochigi Prefecture.