Schwarzburg-Sondershausen was a county until 1697. In that year, it became a principality, which lasted until the fall of the German monarchies in 1918, during the German Revolution of 1918–1919. After the German Revolution, it became a republic.
In 1920, it joined with other small states in the area to form the new state of Thuringia. Schwarzburg-Sondershausen had an area of 862 km² and a population of 85,000 (1905). Towns placed in the state were: Arnstadt, Sondershausen, Gehren, Langewiesen, Großbreitenbach, Ebeleben, Großenehrich, Greußen and Plaue.