Rhineland-Palatinate
The state of Rhineland-Palatinate was founded shortly after the Second World War on 30 August 1946. It was formed mainly from the southern part of the Prussian Rhine Province (the "Regierungsbezirke" of Koblenz and Trier), from Rhenish Hesse, from the western part of Nassau and the Bavarian Rhenish Palatinate minus the county of Saarpfalz. The Joint German-Luxembourg Sovereign Region ("Gemeinschaftliches deutsch-luxemburgisches Hoheitsgebiet") is the only unincorporated area of the state of Rhineland-Palatinate. This condominium is formed by the rivers Moselle, Sauer, and Our, where they run along the border between Luxembourg and Rhineland-Palatinate or the Saarland.
Palatinate (region)
The union with Bavaria was finally dissolved following the reorganisation of German states during the Allied occupation of Germany after World War II. While Bavaria itself was part of the U.S. occupation zone, the Palatinate was occupied by French forces. The French reorganised their occupation zone by founding new states, so that in 1947 the Palatinate was combined with Rhenish Hesse ("Rheinhessen"), the former parts of the People's State of Hesse left of the Rhine, and the southern part of the Prussian Rhine Province, to form the German federal state of Rhineland-Palatinate. The Palatinate formed the administrative district ("Regierungsbezirk") Pfalz. 
This reorganisation came with smaller losses of former district territory to the Saarland, especially in the area of Sankt Wendel. As part of the 1969 administrative reform, some minor border changes were made in the north. The Diocese of Speyer and the Evangelical Church of the Palatinate still exist today largely based on the historic boundaries of the old Bavarian district of "die Pfalz".