Westphalia (; ; ) is a region of northwestern Germany and one of the three historic parts of the state of North Rhine-Westphalia. It has an area of and 7.9 million inhabitants. The territory of the region is almost identical with the historic Province of Westphalia, which was a part of the Kingdom of Prussia from 1815 to 1918 and the Free State of Prussia from 1918 to 1946. In 1946, Westphalia merged with North Rhine, another former part of Prussia, to form the newly created state of North Rhine-Westphalia. In 1947, the state with its two historic parts was joined by a third one: Lippe, a former principality and free state. The seventeen districts and nine independent cities of Westphalia and the single district of Lippe are members of the Westphalia-Lippe Regional Association (Landschaftsverband Westfalen-Lippe). Previous to the formation of Westphalia as a province of Prussia and later state part of North Rhine-Westphalia, the term "Westphalia" was applied to different territories of different sizes such as the western part of the ancient Duchy of Saxony, the Duchy of Westphalia or the Kingdom of Westphalia. The Westphalian language, a variant of the Low German language, is spoken beyond modern Westphalia's borders in neighbouring southwestern Lower Saxony and northwestern Hesse. Geography Landscapes Being a part of the North German Plain, most of Westphalia's north is flat. In the south the German Central Uplands emerge. Westphalia is divided into the following landscapes. Flat to hilly ( and under): East Westphalia, Münsterland, eastern Ruhr Metropolitan Area, Tecklenburg Land, Westphalian Hellweg Hilly to mountainous (up to ): Westphalian part of the Sauerland, Siegerland, Wittgenstein Largest cities Rivers Westphalia is roughly the region in between the rivers Rhine and Weser, located both north and south of the Ruhr River. Other important rivers are the Ems and the Lippe. Mountains The Langenberg () and the Kahler Asten () in the Sauerland part of the Rothaar Mountains are Westphalia's and also North Rhine-Westphalia's highest mountains. Westphalia and Eastphalia The term "Westphalia" contrasts with the much less used term "Eastphalia", which roughly covers the southeastern part of the present-day state of Lower Saxony, western Saxony-Anhalt and northern Thuringia. Division Westphalia is divided into three governmental districts. These are subdivided into further districts and independent cities. All districts and independent cities of the governmental districts of Arnsberg and Münster are considered to be a part of Westphalia as a