It is certain that the Kokubun family of Mutsu Province reigned over the southern area of Miyagi County from the period of the Northern and Southern Courts (Japan) to the Sengoku period (Japan) and, according to the genealogical table of the family, their reign over the Mutsu Province is said to have started when their ancestor Tanemichi governed the Kokubun-sho estate of the region in the Kamakura period.
陸奥国の国分氏は南北朝時代(日本)から戦国時代(日本)末まで宮城郡南部を領したことが確かだが、系図によれば鎌倉時代に国分氏の祖国分胤通が同郡の国分荘を領したのがはじまりだとされる。