Recognizing the importance of this location, after the Battle of Sekigahara, Tokugawa Ieyasu ordered the construction of Sasayama Castle to isolate Toyotomi Hideyori at Osaka Castle from the powerful feudal lords of western Japan, many of whom still had pro-Toyotomi loyalties.

[2] By this style of construction, the fledgling Tokugawa Shogunate bled the powerful western daimyō of wealth and tested their loyalty to the new regime.

To hasten completion of the castle, neither tenshu nor corner yagura watchtowers were constructed, and the castle consisted a central area surrounded by stone walls and a moat.

[3] Almost all of the buildings in the castle were destroyed after the Meiji Restoration, except for the Ōshoin (Grand Hall).

However, the Ōshoin was destroyed during a firebombing air raid by American forces in 1944.