Mauthausen-Gusen concentration camp was the hub of a large group of German concentration camps that was built around the villages of Mauthausen and Sankt Georgen an der Gusen (Gusen) in Upper Austria, roughly 20 kilometres (12 mi) east of the city of Linz. The camp operated from the time of the Anschluss, when Austria was annexed into the German Third Reich in early 1938, to the beginning of May 1945, at the end of the Second World War. Starting with a single camp at Mauthausen, the complex expanded over time and by the summer of 1940 Mauthausen had become one of the largest labour camp complexes in the German-controlled part of Europe, with four main subcamps at Mauthausen and nearby Gusen, and nearly 100 other subcamps located throughout Austria and southern Germany, directed from a central office at Mauthausen.