Smallest of the Ernestine duchies, re-created in the 1826 redistribution of the Saxon lands when the Hildburghausen line exchanged its duchy for Altenburg; two detached blocks of unusually rich farmland east and west of Reuss.
Became a republic in November 1918; the Free State of Saxe-Altenburg was merged into the State of Thuringia in 1920.
Standard Oxford History of Modern Europe volume covering exactly the 1815-1866 settlement and the Kleinstaaten's survival that created and preserved this duchy; used because no polity-specific English monograph exists (verified on Open Library, ISBN 9780198204329).