Rhineland-Palatinate is one of the 16 states of the Federal Republic of Germany. It has an area of 19,846 square kilometres (7,663 sq mi) and about four million inhabitants. The capital is Mainz. English speakers also commonly refer to the state by its German name, Rheinland-Pfalz. The state of Rhineland-Palatinate was established on 30 August 1946. It was formed from the northern part of the French Occupation Zone, which included parts of Bavaria (the Rhenish Palatinate), the southern parts of the Prussian Rhine Province (including the District of Birkenfeld which formerly belonged to Oldenburg), parts of the Prussian Province of Nassau (see Hesse-Nassau), and parts of Hesse-Darmstadt (Rhinehessen on the western banks of the Rhine); the constitution was legally confirmed by referendum on 18 May 1947.