Honda Tadakatsu
The name of Isumi District was standardized to its present "kanji" and pronunciation by the Edo period. Tokugawa Ieyasu (1543–1616), as part of the wider unification of Japan, entered the Kantō region in 1590 and awarded the Isumi District to a trusted general Honda Tadakatsu (1548–1610). Under the Tokugawa shogunate, the minor feudal domain of Ōtaki Domain, controlled by Honda Tadakatsu from Ōtaki Castle, controlled 18 villages within the district, with another 57 villages under the control of other domains (including one village belonging to Nitta Domain in Tosa Province). The remaining 108 villages were "tenryō" under direct control of the central government and administered by various hatamoto, or samurai in the direct service of the Tokugawa shogunate. The Edo period was marked by the extensive development of rice paddy land in the district.