The state capital of North Rhine-Westphalia has a diverse transportation history. Düsseldorf is one of the cities that was introduced to the still young mode of transport, the railway, very early on with the Düsseldorf-Elberfeld Railway in 1838. The Rheinische Bahngesellschaft (Rheinbahn) established itself in urban public transport starting in 1898, gaining recognition far beyond the city limits. As a city on the Rhine, Düsseldorf has historically held the status of a port city. The international airport, which opened in 1927, is the third largest in Germany. With the connection to the S-Bahn in 1967, the Rhine metropolis is considered a pioneer in the development of an efficient S-Bahn system along the Rhine and Ruhr. In 1981, the city railway finally goes underground, marking the beginning of the subway era in Düsseldorf.