Principality of Salm
The Principality of Salm was ruled jointly by the princes of Salm-Kyrburg and Salm-Salm, Frederick IV, Prince of Salm-Kyrburg, and Constantine, Prince of Salm-Salm; each line had equal sovereign rights, but neither had a separate territory. Salm became independent and joined the Confederation of the Rhine in 1806. It was annexed by France in 1811. Its territory was given to Prussia by the Congress of Vienna in 1815; it became the westernmost part of the Prussian Province of Westphalia. In 1871, The German Empire used a flag identical to Salm's tricolour flag.