A Shingun (also called a Kamikori) is a special district type that came into existence with the establishment of the Kokugun system, and is considered to be the holly precincts of a shrine (domain of a kami), and differs from other types of districts. The Kokugun system was established by the Taika Reforms, and the Shingun system was established in the year 649.
The origins of Ise Shingun are derived from the mythological days when Owakugo-no-mikoto, a descenant of Amenohiwake-no-mikoto bestowed upon Amaterasu Omikami of the lands, 'Shinkoku' (no relation to later concepts called 'shinkoku') east of the Isobe-gawa River (however, it is said that the river is actually the Shitahi-ogawa River). After the establishment of the Shingun, it was divided into Watarai-no-kori and Take-no-kori, which were subsequently renamed as Watarai-gun (written with different characters for "Watarai") and Taki-gun. In the year 664 Iino-gun was separated from Taki-gun, and made a Koryo (an Imperial demesne). In the year 889, however, Emperor Uda again donated the said gun to the Ise-jingu Shrine for a span of one generation only, and when it was decided that Emperor Uda would abdicated and Emperor Daigo acceded to the throne in 897, the said gun was permanantly returned to the Shingun. That is the reason that the abovementioned three gun, in particular, are called the 'Jinsangun' (three districts of the Jingun).
Subsequently, accompanying the rise to prominence of the Shinkoku ideology (thought of Japan as the land of the gods), one gun after another in Ise Province was incorporated into the Shingun.
974: Ano-gun (Ise Province)
From the later part of the Heian Period, influential members of the aristocracy and prominent temples and shrines established shoen (manor in medieval Japan) within the precincts of the Ise-jingu Shrine, whereby the actual lands in the precincts of the Jingu became encroached upon. When a 'Kamikaze' proclamation was issued because of a Mongol invasion of Japan, the Kamakura Bakufu (Japanese feudal government headed by a shogun) meritoriously promulgated an 'Estate Recovery Act', which was a type of Tokuseirei (an order for the return of sold land and the dissolution of debts), whereupon all such estates were siezed and returned to the Ise-jingu Shrine. The famous Einin no Tokuseirei for gokenin (an immediate vasal of the shogunate in the Kamakura and Muromachi through Edo periods) was abolished after a period of one year; however, this order was not abolished as a shield against the 'risk of divine punishment'.
List of Shingun
Munakata-gun, Chikuzen Province: Munakata Taisha Shrine
Watarai-gun, Ise Province: Ise-jingu Shrine
Taki-gun, Ise Province: Ise-jingu Shrine
Awa-gun, Awa province: Awa-jinja Shrine
O-gun, Izumo Province: Kumano-jinja Shrine, Izumo Taisha Shrine
Kashima-gun, Hitachi Province (Ibaraki Prefecture): Kashima-jingu Shrine
Katori-gun, Shimousa province: Katori-jingu Shrine
Nagusa-gun, Kii Province: Hinokuma-jingu Shrine, Kunikakasu-jingu Shrine