The Principality of Salm was created in 1632 as a state of the Holy Roman Empire, and re-created in 1803 in order to compensate the princes of Salm-Kyrburg and Salm-Salm, who had lost their states to France in 1793–1795.

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;[1] each line had equal sovereign rights, but neither had a separate territory.

[2] Salm became independent and joined the Confederation of the Rhine in 1806.

Its territory was given to Prussia by the Congress of Vienna in 1815; it became the westernmost part of the Prussian Province of Westphalia.

[3] It covered approximately the same area as the present-day District of Borken.