Districts of Japan
The district (郡 gun ) was used as an administrative unit in Japan between 1878 and 1921 and is roughly equivalent to the county of the United States, ranking at the level below prefecture and above city, town or village. As of 2008, cities belong directly to prefectures and are independent from districts. In Japan towns and villages belong to districts and the districts possess little to no administrative authority. The districts are used primarily in the Japanese addressing system and to identify the relevant geographical areas and collections of nearby towns and villages.
The district was initially called kōri and has ancient roots in Japan. Although the Nihon Shoki says they were established during the Taika Reforms, kōri was originally written 評. It was not until the Taihō Code that kōri came to be written 郡. Under the Taihō Code, the administrative unit of province (国; kuni) was above district, and the village (里; sato or 郷; sato) was below.
Confusing cases in Hokkaidō 
Because district names had been unique within a single province and as of 2008 prefecture boundaries are roughly aligned to provincial boundaries, most district names are unique within their prefectures.
Hokkaidō Prefecture, however, came much later to the ritsuryō provincial system, only a few years before the prefectural system was introduced, so its eleven provinces included several districts with the same names:
- Three Kamikawa Districts and two Nakagawa Districts in the Hokkaidō Prefecture. Each jurisdiction refers to its geographical position along the river from which the former province, and subsequent subprefecture, takes its name. "Kamikawa" means upper course of the river; "Nakagawa" means middle course.
- Kamikawa Dist. (Ishikari), managed by the Kamikawa Subprefecture
- Kamikawa Dist. (Teshio), managed by the Kamikawa Subprefecture
- Kamikawa Dist. (Tokachi), managed by the Tokachi Subprefecture
- Nakagawa Dist. (Teshio), managed by the Kamikawa Subprefecture
- Nakagawa Dist. (Tokachi), managed by the Tokachi Subprefecture
- Abuta District, Rumoi District, Sorachi District, and Yufutsu District are similar, but each of them is a single district allotted to two subprefectures.
See also 
|Administrative divisions of Japan|
- "Japan's Evolving Nested Municipal Hierarchy: The Race for Local Power in the 2000s," by A.J. Jacobs at Urban Studies Research, Vol. 2011 (2011); doi:10.1155/2011/692764
- Graphic shows relationships among Japanese cities at p. 7 of "Large City System of Japan"
- Text of the Local Government Law (Japanese)