Mogami is located in the mountains of extreme north eastern Yamagata Prefecture. Despite its name, the Mogami River does not run through the town. The area is known for extremely heavy snows in winter.
During the Sengoku period, the area was under the control of the Mogami clan who built Oguni Castle. During the Edo period, parts of the area came under the control of Shinjō Domain. After the start of the Meiji period, the area became part of Mogami District, Yamagata Prefecture. The villages of Higashi-Oguni and Nishi-Oguni were established on April 1, 1889. These villages were merged to form the town of Mogami on September 1, 1954.
Mogami was formerly known as a horse breeding area, and numerous ranches supplied horses to the Imperial Japanese Army's cavalry regiments. Modern Mogami is dependent on agriculture, forestry and seasonal tourism to its many hot spring resorts.