Much of
Dewa Province was controlled by the powerful
Mogami clan during the
Sengoku period. After
Toyotomi Hideyoshi assigned the
Uesugi clan to
Aizu, senior Uesugi retainer
Naoe Kanetsugu established himself at the neighboring
Yonezawa Domain, with an army of 20,000 and gradually expanded his control north into Mogami territory. However, with the help of the
Date clan under
Date Masamune, the Mogami were able to defend Yamagata until Naoe was forced to withdraw following the defeat of the pro-Toyotomi forces at the
Battle of Sekigahara. During the
Tokugawa shogunate, in 1600, the Mogami were initially confirmed in their holdings, with an assessed income of 570,000
koku, which was the 5th largest domain in Japan at the time. However, with after the death of
Mogami Yoshiaki, the clan underwent a number of inheritance struggles, and was dispossessed by the Tokugawa shogunate, and a much reduced Yamagata Domain (220,000
koku) was then assigned to the
Torii clan in 1622. Torii Tadatsune died without an heir in 1636, and Yamagata was reassigned to
Hoshina Masayuki (with a further reduction to 200,000
koku) until he was assigned to rule
Aizu Domain in 1643. Reduced further to 150,000
koku, and then to 100,000
koku and finally to 60,000
koku, domain was then ruled by several branches of the
Matsudaira clan or the
Okudaira clan, subsidiary branches of the shogunal Tokugawa clan from 1643 to 1764. The domain had a population of 13,032 people in 2157 households per the 1697 census. The domain maintained its primary residence (
kamiyashiki) in
Edo at Daimyō-kōji, in
Marunouchi. In 1767, Yamagata Domain was assigned to the
Akimoto clan, formerly of
Kawagoe Domain, who ruled for four generations until 1845. During the
Bakumatsu period, the domain was assigned to its final rulers, the
Mizuno clan. It was now reduced to only 50,000
koku.
Mizuno Tadakiyo served as
Jisha-bugyō and
wakadoshiyori in the shogunal administration and in 1862, became a
rōjū in the service of
Shōgun Tokugawa Iemochi. During the
Boshin War, Yamagata Domain was a member of the
Ōuetsu Reppan Dōmei; although its final daimyō, Mizuno Tadahiro was only 13 years old. The domain switched sides to the pro-Imperial forces in June 1869. The new
Meiji government seized the domain, and exiled Mizuno Tadahiro to a newly created 50,000
koku Asahiyama Domain in
Ōmi Province in 1870. With the
abolition of the han system in July 1871, the former Yamagata Domain became the nucleus of the new Yamagata Prefecture. ==List of
daimyōs==