Naruto-machi(12404), Sambu-machi(12405), Hasunuma-mura(12406) and Matsuo-machi(12407) in Sambu-gun are merged, and Sammu-shi(12237) is newly established.
成東町(12404)、山武町(12405)、蓮沼村(12406)、松尾町(12407)が合併し、山武市(12237)を新設