The keep 天守閣 (tenshukaku), which was completed in the late sixteenth century, maintains its original wooden interiors and external stonework.

[1] Its complete defences would have included an extensive system of inter-connecting walls, moats, and gatehouses.

A fortification was built at this location by the shugō of Shinano Province, Shimadachi Sadanaga of the Ogasawara clan during the Eisho era (1504–1520).

With the assassination of Oda Nobunaga in 1582, the castle was seized by Ogasawara Dosetsuzai with the backing of Uesugi Kagekatsu.

Following Toyotomi Hideyoshi's conquest of Odawara in 1590, Tokugawa Ieyasu was transferred from his ancestral domains to the Kantō region, and Ishikawa Kazumasa was placed in charge of Matsumoto.

The loss of this building decided the location in favor of Nagano city, and the Matsumoto District Court was built on the site in 1878.

It was because of neglect coupled with a structural defect, but many people believed the tower leaned due to the curse of Tada Kasuke.

[5] A local high school principal, Kobayashi Unari, decided to renovate the castle and appealed for funds.

The five surviving original structures in the main keep complex ( Tenshu, Inui-ko-tenshu (small northern tower), Watari-yagura (roofed passage), Tatsumi-tsuke-yagura (southern wing), and Tsukimi-yagura (moon-viewing room) ) were designated as National Treasures of Japan in 1952.

This enabled access to government funding for a major restoration project from 1950 to 1955, during which these buildings were dismantled and rebuilt.