There were two Okumiya shrines on the side of Iwakura (Shrine built on the top of a mountain as a worship space), Ushio shrine and Sannomiya shrine, and the present East shrine was first established as Satomiya shrine (shrine built in village area as a worship space) of Ushio Shrine in B.C. 91.
磐座を挟んで2社の奥宮（牛尾神社・三宮神社）があり、現在の東本宮は崇神天皇7年に牛尾神社の里宮として創祀されたものと伝えられている。