Built in 1602 after seven years of construction, Karatsu-jō was set up by Terasawa Hirotaka, a former retainer of Toyotomi Hideyoshi. According to some sources, part of the original castle's materials were taken from nearby Nagoya-jō (Hideyoshi's base of operations for the Korean invasions - not to be confused with Aichi's much larger Nagoya-jō), which was demolished following the ascendancy of Tokugawa Ieyasu. The castle changed hands numerous times across the Edo period, from the Terasawa clan to the Matsudairas, then the Doi, Mizuno and Ogasawara clans respectively. Like in many other cases across the country, the castle was torn down in 1871 following the Meiji Restoration and the grounds turned into Maizuru-kōen in 1877. The present donjon dates from October of 1966, but it is thought that the intended tenshu was never actually built, only the foundations for one.