Mogami Yoshiaki History Museum

The Mogami Yoshiaki History Museum is a historical museum located along Kōen-dōri (Park Street) in Ōtemachi, Yamagata City, Yamagata Prefecture, near Kajō Park (the site of Yamagata Castle). It mainly collects and exhibits materials related to Mogami Yoshiaki, the Sengoku-period daimyō who laid the foundations of the Yamagata domain, and serves as a base for preserving valuable historical materials associated with the Mogami family, including armor, swords, ancient documents, and paintings. It is located in Ōtemachi, which corresponds to the former third enclosure (san-no-maru) of Yamagata Castle, and its location also makes it convenient for tourists visiting Kajō Park to stop by while strolling through the castle ruins.

Collection

One of the central items in the collection is the “sanjūhachi-ken sōfukurin suji-kabuto” (38-plate ridged helmet with fully rimmed ridges), used by Lord Mogami Yoshiaki, a helmet traditionally said to have been worn by Yoshiaki at the Battle of Hasedō in 1600 (Keichō 5). In addition, the museum holds a broad range of paintings and furnishings, including relics such as an iron command baton traditionally said to have belonged to Yoshiaki, the folding screen of the Battle of Hasedō depicting the scene at the time of the battle, and fusuma (sliding-door) paintings handed down from Yamagata Castle. A distinctive feature is that the museum systematically holds materials conveying the warrior culture of the Mogami family's 570,000-koku era, centered on swords and armor.

Exhibitions

In addition to its permanent exhibition, the museum holds corner exhibitions on swords and armor from time to time, and may also organize special exhibitions introducing works by swordsmiths connected to Dewa Province (present-day Yamagata Prefecture) and by contemporary swordsmiths. From April 2 to July 5, 2026, for example, a corner exhibition titled “Kurogane no Bi 2026: The ‘Three Masters of Dewa’ and Modern Craftsmen” was held, and the museum continues to convey the region's sword culture. Because the collection items are rotated along with changes in display, the museum is structured so that visitors can encounter different historical materials depending on when they visit.

Access

Closed on Mondays (on the following day if a Monday coincides with a national holiday), and also closed during exhibition-changeover periods and over the New Year holidays. Admission has been free since April 2009 (Heisei 21). There is no dedicated parking lot, but visitors can use the adjacent Ōtemachi Parking Lot (fee-based) or the parking facilities within Kajō Park. The location is easily accessible from central Yamagata City.

Regional Culture

Mogami Yoshiaki was a Sengoku-period daimyō who governed Yamagata in Dewa Province, and he is also known as the uncle of Date Masamune. He is known for his achievement of repelling the invasion of the Uesugi army at the Battle of Hasedō, one of the largest battles in the Tōhoku region, which was linked to the Battle of Sekigahara. As a figure who laid the foundations of the Yamagata castle town, he remains a symbol of Yamagata's regional history and warrior culture to this day.