To begin with, Shiba-gun County of Mutsu Province is said to have been the origin of the family name of the Shiba clan, so the Oshu region was the birthplace for the Shiba clan.
そもそも斯波氏の名乗りの起源は陸奥紫波郡とされており、奥州は斯波氏にとっては本貫である。