The Rhenish Republic, proclaimed October 1923 in the German Rhineland, is better viewed as an aspiration than as a republic. A manifestation of the short-lived separatist movement that arose in the Rhineland during the turbulent years following Germany's defeat in the First World War, the Rhenish Republic, as proclaimed, comprised three territories, named North, South and Ruhr with regional capitals respectively in Aachen / Aix-la-Chapelle, Koblenz and Essen.
Germany had been united and ruled from Berlin for less than sixty years, and in the Rhineland as elsewhere blame for the disaster of the World War defeat was variously apportioned to the military, the (German) government or indeed the French whose troops would remain in occupation of the left bank of the Rhine till 1930. It is generally accepted that the French, whose troops occupied the left bank of the Rhine, encouraged anti-Berlin separatism in the area during the period that followed the Versailles settlement.
As the 1920s progressed, a measure of brittle stability returned to Germany under the Weimar State: Rhenish separatism, never a mass movement, faded. The French military occupation of the Ruhr region initiated January 1923 to enforce reparations payments was withdrawn in the summer of 1925, following the agreement in September 1924, under the Dawes Plan, of a slightly less punitive reparations régime. The de facto demise of the Rhenish Republic can be dated at February 1924 when the movement's leader Hans Adam Dorten 1880 - 1963 was obliged to flee to France.
For later generations the episode is hard to disentangle from all the other manifestations of economic hardship and political instability characterising the region at the time: the Rhenish Republic is today remembered in the Anglosphere largely (if at all) because of the active support Rhenish separatism received in the 1920s from the mayor of Cologne, an unapologetic Rhenish partisan, who succesfully campaigned for the installation of West Germany's government at Bonn: Bonn would hold it's status in West Germany as the provisional German capital from 1949 until 1990.