In the han system, Oyumi was a political and economic abstraction based on periodic cadastral surveys and projected agricultural yields. In other words, the domain was defined in terms of kokudaka, not land area. This was different from the feudalism of the West.
Oyumi Domain was created in February, 1627, when Morikawa Shigetoshi, a hatamoto in the service of Shogun Tokugawa Hidetada acquired holdings in Sagami, Kazusa and Shimōsa Provinces with revenues exceeding the 10,000 koku necessary to qualify as a daimyō. He was allowed to build a jin'ya on the site of the Sengoku period Oyumi Castle. He later rose to the post of Rōjū and his successors continued to rule Oyumi Domain until the Meiji Restoration.
List of daimyō
|#||Name||Tenure||Courtesy title||Court Rank||revenues|
|1||Morikawa Shigetoshi ( 森川重俊?)||1627–1632||Dewa-no-kami||Lower 5th (従五位下)||10, 000 koku|
|2||Morikawa Shigemasa ( 森川重政?)||1632–1663||Iga-no-kami||Lower 5th (従五位下)||10,000 koku|
|3||Morikawa Shigenobu ( 森川重信?)||1663–1692||Dewa-no-kami||Lower 5th (従五位下)||10,000 koku|
|4||Morikawa Shigetane ( 森川俊胤?)||1692–1732||Dewa-no-kami||Lower 5th (従五位下)||10,000 koku|
|5||Morikawa Shigetsune ( 森川俊常?)||1732–1734||Naizen-no-kami||Lower 5th (従五位下)||10,000 koku|
|6||Morikawa Shigenori ( 森川俊令?)||1734–1764||Naizen-no-kami||Lower 5th (従五位下)||10,000 koku|
|7||Morikawa Shigetaka ( 森川俊孝?)||1764–1788||Kii-no-kami||Lower 5th (従五位下)||10, 000 koku|
|8||Morikawa Shigetomo ( 森川俊知?)||1788–1838||Naizen-no-kami||Lower 5th (従五位下)||10,000 koku|
|9||Morikawa Shigetami ( 森川俊民?)||1838–1855||Dewa-no-kami||Lower 5th (従五位下)||10,000 koku|
|10||Morikawa Shigehira ( 森川俊位?)||1855–1858||Dewa-no-kami||Lower 5th (従五位下)||10,000 koku|
|11||Morikawa Shigenori ( 森川俊徳?)||1858–1862||Dewa-no-kami||Lower 5th (従五位下)||10,000 koku|
|12||Morikawa Shigekata ( 森川俊方?)||1862–1871||Naizen-no-kami||Lower 5th (従五位下)||10,000 koku|
The site of the Oyumi Domain jin'ya is now under a residential area of the city of Chiba.
- Mass, Jeffrey P. and William B. Hauser. (1987). The Bakufu in Japanese History, p. 150.
- Elison, George and Bardwell L. Smith (1987). Warlords, Artists, & Commoners: Japan in the Sixteenth Century, p. 18.
- Bolitho, Harold (1974). Treasures among men; the fudai daimyo in Tokugawa Japan. New Haven: Yale University Press.
- Kodama Kōta 児玉幸多, Kitajima Masamoto 北島正元 (1966). Kantō no shohan 関東の諸藩. Tokyo: Shin Jinbutsu Ōraisha.