Excavations at the Tagumaishihata site began in April 2008 ahead of a private development project, and a settlement centered on the Yayoi period was discovered across the entire survey area of approximately 31,000 square meters. Among other things, the site produced significant results, including the discovery of the burial grounds of a group of influential people from the first half of the middle Yayoi period (2nd century BC), which was not initially anticipated, and the unearthing of a total of 15 bronze weapon-shaped artifacts as grave goods from the six tombs surveyed. As this is an extremely important site, showing that the Munakata tribe, located on the eastern edge of the Genkai Sea, had grown into one of the most influential groups in northern Kyushu during the Yayoi period, it was designated a national historic site on February 22, 2010.