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TheGrand Duchy of Oldenburg was a state in Europe. It was in the area that today isGermany. It was created out of the smallerDuchy of Oldenburg. The state was created at theCongress of Vienna in1814 but ceased to exist after the German Revolution in1918. The capital of the state wasOldenburg. The Grand ducal family lived at theSchloss Oldenburg in the capital. They hadCounts, dukes and grand dukes of Oldenburg