Parts of the city are within the borders of Oze National Park or the Echigo Sanzan-Tadami Quasi-National Park Uonuma has a humid subtropical climate (Köppen Cfa) characterized by warm, wet summers and cold winters with heavy snowfall.

During the Edo period, the area was largely tenryō territory administered directly by the Tokugawa shogunate or part of the holdings of Aizu Domain.

After the Meiji restoration, the area was organised as part of Kitauonuma District, Niigata with the creation of the modern municipalities system.

The modern city of Uonuma was established on November 1, 2004, from the merger of the towns of Horinouchi and Koide, and the villages of Hirokami, Irihirose, Sumon and Yunotani (all from Kitauonuma District).

Uonuma has a mayor-council form of government with a directly elected mayor and a unicameral city legislature of 20 members.