Around 1930: Many earthenware and stone tools were found during the construction of National Railway Aniai Line (present Akita Inland Railway).
July-December 1992: Survey by the Akita Prefectural Board of Education (which made it know to the general public)
November 1994: Field survey by the Akita Archaeological Center on the proposed road construction site
May 1995: Excavation started by the Akita Archaeological Center. Discovery of Stone Circle A.
June 1995: Discovery of Stone Circle B.
January 1996: The Akita Prefectural Board of Education and the Civil Engineering Bureau of Akita Prefectural Government considered moving the circle stones for conservation.
August 1996: Field survey started.
October 1996: Takanosu Town Cultural Property Conservation Council advised Takanosu Town to conserve the site at the original location. Takanosu Town requested the Civil Engineering Bureau of Akita Prefectural Government for modification of the road construction plan and conservation of the site at the original location. Discovery of Stone Circle C by hand boring.
November 1996: Decision by the Akita Prefectural Government to conserve the site on the spot by changing the course of the planned new road.
April 1997: Authority for management of the site was moved to Takanosu Town.
June 1997: Detailed field survey was started by Takanosu Town.
July 1997: Takanosu Cultural Archaeological Site Working Group established (later renamed Isedotai Site Working Group).
June 1998: Isedotai Site Research Supervision Committee was established.
September 1999: Discovery of a 100-meter long ditch crossing the site.
August 2000: Discovery of Stone Circle D by hand boring to the south of Stone Circle C. Field survey by the National Agency of Cultural Affairs for state designation of the site as a historic site.
October 2000: The Minister of Education requested the Council for the Protection of Cultural Properties for opinions on the values of the Isedotai Site.
November 2000: The Council for the Protection of Cultural Properties advised the Minister for Education that “this site is of extreme importance as a typical site of rituals during the late Jomon period (about 4000 years ago) with various religious and ritualistic facilities such as more than one stone circles, buildings, and graves and also with remains of buildings of civil engineering techniques of the time.”
January 2001: The state designation of the Isedotai Site was announced on the official bulletin.
April 2001: The 1st phase of excavation started (mostly in the stone circles’ zone).
June 2001: The 1st Jomon Festival (to be held every year since then)
March 2005: Takanosu Town merged with Moriyoshi Town, Aikawa Town, and Ani Town, to become part of Kita-Akita City.
April 2008: The 2nd phase of excavation started (mostly on the eastern side of the plateau).
April 2011: The 1st phase of the site rearrangement started. The 1st Return-of-Jomon-Salmon Festival started (to be held every year since then).
May 2015: Free guide tours with elderly volunteers started.
April 2016: The Isedotai Jomon Museum was opened.
December 2019: The Isedotai Site was included in the national recommendation of a world heritage site to UNESCO.
July 2021: The Isedotai Site was included in the UNESCO list of World Cultural Heritage sites.
