Dortmund is the third-largest city in North Rhine-Westphalia after Cologne and Düsseldorf, and the eighth-largest city of Germany, with a population of 588,250 inhabitants as of 2021. It is the largest city of the Ruhr, Germany's largest urban area with some 5.1 million inhabitants, as well as the largest city of Westphalia. On the Emscher and Ruhr rivers, it lies in the Rhine-Ruhr Metropolitan Region and is considered the administrative, commercial, and cultural center of the eastern Ruhr. Dortmund is the second-largest city in the Low German dialect area after Hamburg.
Founded around 882, Dortmund became an Imperial Free City. Throughout the 13th to 14th centuries, it was the "chief city" of the Rhine, Westphalia, and the Netherlands Circle of the Hanseatic League. During the Thirty Years' War, the city was destroyed and decreased in significance until the onset of industrialization. The city then became one of Germany's most important coal, steel and beer centres. Dortmund consequently was one of the most heavily bombed cities in Germany during World War II. The devastating bombing raids of 12 March 1945 destroyed 98% of buildings in the inner city center.