On February 20, 2006 the city of Mizusawa merged with the city of Esashi and the municipalities of Maesawa, Isawa and Koromogawa from Isawa District to form the new city of Oshu. As of 2003, the city had an estimated population of 60,979 and a population density of 629.17 persons per km². The total area was 96.92 km². The city was founded on April 1, 1954.