North Rhine-Westphalia (German: Nordrhein-Westfalen) is the most populous state of Germany, as well as the fifth largest by area. North Rhine-Westphalia was formed in 1946 as a merger of the northern Rhineland and Westphalia, both formerly parts of Prussia. Its capital is Düsseldorf; the biggest city is Cologne. Four of Germany's ten biggest cities — Cologne, Düsseldorf, Dortmund, and Essen — are located in North Rhine-Westphalia.