Gelsenkirchen was first mentioned in 1150, but it remained a tiny village until the 19th century, when the Industrial Revolution led to the growth of the entire area. In 1840, when the mining of coal began, 6000 inhabitants lived in Gelsenkirchen; in 1900 the population had increased to 138,000.
In the early 20th century Gelsenkirchen was the most important coal mining town of Europe. It was called the "city of thousand fires", due to the burning stacks. In 1928 Gelsenkichen was merged with the adjoining cities of Buer and Horst. The city bore the name Gelsenkirchen-Buer, until it was renamed to Gelsenkirchen in 1930. During the Nazi era Gelsenkirchen was a centre of weapon and ammunition production; for this reason it was completely bombed down by allied air raids in World War II.
Most collieries are closed now. Gelsenkirchen is searching for a new image. Today the largest solar cell plant of Germany is located in the city. Gelsenkirchen is home of the successful football club FC Schalke 04.