Jingū at Isë famously has two main sanctuaries, the Inner Sanctuary enshrining Amaterasu Ōmikami, and the the Outer Sanctuary enshrining Toyoukë Ōmikami. However, the whole complex consists of 125 jinja, some of which are just sacred stones, and some of which are several miles from the Inner and Outer Sanctuaries. The most important of these jinja are called the “Betsugū”, or “Other Sanctuaries”. Some of these are ancient, and may have been earlier sites of the main sanctuaries. Two, enshrining kami associated with winds, were upgraded to Betsugū after an attempted Mongol invasion of Japan was prevented by a divine wind (“kami kazë”).
One of them, Yamatohimë no Miya, is one hundred years old today.
I think this makes it the youngest of the jinja that are part of Jingū, by a substantial margin. The ages of the others are not always clear, but they were around by the eighteenth century, as far as my reading has suggested. It may also be the only one of the jinja that has a clear and well-attested foundation date.
Yamatohimë no Miya enshrines Yamatohimë no Mikoto, the (mythical) daughter of the (mythical) Suinin Tennō, who brought Amaterasu Ōmikami from Yamato Province (modern Nara Prefecture) to Isë Province (modern Mië Prefecture), following a very indirect route that took her through much of central Japan. There are a number of jinja that claim to have been temporary residences for Amaterasu Ōmikami, including some of the other Betsugū, but the final location was determined by an oracle from Amaterasu Ōmikami.
The reasons for the existence of this myth are unclear. Versions appear in the Kojiki and Nihonshoki, so it is as old as these things get, but the journey is longer in later versions. It does not seem to have any mythical function, so I think there is likely to be some historical basis for it, but it is completely unclear what that basis was. (There is a mythical reason for moving Amaterasu Ōmikami out of the imperial residence, but not for having her wander around Japan for years before choosing somewhere to live.)
In any case, it makes Yamatohimë no Mikoto a vital figure in the history of Jingū, and she was always regarded as important, with medieval and early modern scholars trying to pinpoint her grave. There does seem to have been recurring concern over the fact that she was not venerated, and this came to a head in the early twentieth century. At this point, the local government and residents of Isë City petitioned the government to license a jinja to venerate her. It seems that they were (pleasantly) astonished when the Tennō ordered the creation of a new Betsugū to do so.
In this centenary year, Jingū is running a number of commemorative events, including an exhibition at its history museum, which is conveniently close to the jinja itself. There was an article about it in the October 23rd issue of Jinja Shinpō, and it looks interesting — although I doubt I will get to it. Isë is just a bit too far away.
I suspect that a lot of people who do not read the pamphlets think that Yamatohimë no Miya was founded shortly after Yamatohimë no Mikoto’s death, but it is a representative example of jinja to important mythical or historical figures that were established much later. Many of them were established in the Meiji or Taishō periods (late nineteenth and early twentieth centuries), although some are substantially older, and others have older origins but changed greatly in that period. These jinja are one of the ways in which Shinto has changed over the centuries, but with strong roots in its past practice.