Koshi

Koshi was a district of Echigo in which the Nagao family's branch established a political base at Zaōdō during the Muromachi period. Tochio Castle also belonged to the Koshi Nagao. The young Nagao Kagetora, later Uesugi Kenshin, used Tochio as a base while asserting authority over neighbouring warriors in the sixteenth century. A letter to Jōanji from 1551 recalls fighting during his residence there.

Under Tokugawa rule, power shifted to the castle town of Nagaoka. In 1618 Makino Tadanari replaced Hori Naoyori and continued construction of its castle. The new domain began with an assessed income of 62,000 koku, later enlarged to 74,000. Nagaoka's merchants profited from their control of Shinano River transport, although that privileged position also brought disputes with other communities along the river. Castle government and commercial traffic thus reshaped the old district's political landscape.