Essen is a city in North Rhine-Westphalia, Germany. Its population of approximately 589,000 makes it the ninth-largest city in Germany. It is the central city of the northern part of the Rhine-Ruhr metropolitan area and seat to several of the regions authorities. Founded around 845, Essen remained a small town within the sphere of influence of an important ecclesiastical principality until the onset of industrialization. The city then — especially through the Krupp family iron works — became one of Germanys most important coal and steel centers. Essen, until the 1970s, attracted workers from all over the country; it was the 5th-largest city in Germany between 1929 and 1988, peaking at over 730,000 inhabitants in 1962. Following the region-wide decline of heavy industries in the last decades of the 20th century, the city has seen the development of a strong tertiary sector of the economy. Essen today is seat to 13 of the 100 largest German corporations, including two DAX corporations, placing the city second only to Munich and on-par with Frankfurt am Main in number of corporate headquarters. Although it is the most indebted city in Germany, Essen continues to pursue its redevelopment plans. Notable accomplishments in recent years include the title of European Capital of Culture on behalf of the whole Ruhr area in 2010 and the selection as the European Green Capital for 2017. In 1958, Essen was chosen to serve as the seat to a Roman Catholic diocese. In early 2003, the universities of Essen and the nearby city of Duisburg were merged into the University of Duisburg-Essen with campuses in both cities and a university hospital in Essen.