Gelsenkirchen was first documented 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 in Europe. It was called the "city of thousand fires", due to the burning stacks. In 1928 Gelsenkirchen 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 remained a centre of coal production and oil refining, and for this reason it was bombed by Allied air raids in World War II. Most of the city's collieries are now closed and Gelsenkirchen is searching for a new image. Today Germany's largest solar power plant is located in the city.
