Saxe-Gotha-Altenburg [SEP] dissolved or abolished
of the Gotha Observatory established in 1787.
Nevertheless, when the last dukes Emil August, a fervent admirer of the rise of Napoleon, and his brother Frederick IV had both died without male heirs, the house of Saxe-Gotha-Altenburg finally became extinct in 1825 and quarrels arose between the three remaining Ernestine lines about the succession. As a result of an arbitration issued by King Frederick Augustus I of Saxony in 1826, the Ernestine duchies were rearranged and Saxe-Gotha-Altenburg was again split: 
- Saxe
union between Saxe-Gotha and Saxe-Coburg was dissolved on 12 April 1919 and they formed their own free states.
The governments of Saxe-Altenburg, Saxe-Coburg and Gotha, Saxe-Gotha, Saxe-Meiningen, Saxe-Weimar-Eisenach, Schwarzburg-Rudolstadt, Schwarzburg-Sondershausen and the Republic of Reuss took part in negotiations about a merger of all Thuringian states, if possible including the Prussian elements. But because Prussia was not prepared for any kind of land exchange, the founding of the state