The two surviving lines of the ancient Thuringian house of Schwarzburg — Sondershausen and Rudolstadt — jointly held one shared inheritance of an upper and a lower barony; imperial princes from 1697, sovereign from 1807, and both federal principalities of the German Empire.
Both principalities were proclaimed republics in November 1918 and were merged into the new State of Thuringia in 1920. The Sondershausen line had already died out in 1909, leaving Rudolstadt's prince ruling both.
Covers the Imperial-Estate status and 1697 princely elevation of Thuringian counts within the Reich; used because no English-language monograph on Schwarzburg exists (verified on Open Library, ISBN 9780199688838).