Mauthausen Concentration Camp (known from the summer of 1940 as Mauthausen-Gusen Concentration Camp) grew to become a small group of Nazi concentration camps that was built around the villages of Mauthausen and Gusen in Upper Austria, roughly 20 kilometres (12 mi) east of the city of Linz.
Its history ran from the time of the Anschluss in 1938 to the last week of the Second World War. The largest prisoner of war contingent was Soviet, the second largest was Spanish.
Initially a single camp at Mauthausen, it expanded over time and by the summer of 1940, the Mauthausen-Gusen had become one of the largest labour camp complexes in German-controlled Europe.
Apart from the four main sub-camps at Mauthausen and nearby Gusen, more than 50 sub-camps, located throughout Austria and southern Germany, used the inmates as slave labour. Several subordinate camps of the KZ Mauthausen complex included quarries, munitions factories, mines, arms factories and Me 262 fighter-plane assembly plants.
In January 1945, the camps, directed from the central office in Mauthausen, contained roughly 85,000 inmates.
The death toll remains unknown, although most sources place it between 122,766 and 320,000 for the entire complex. The camps formed one of the first massive concentration camp complexes in Nazi Germany, and were the last ones to be liberated by the Allies. The two main camps, Mauthausen and Gusen I, were labelled as "Grade III" (Stufe III) camps, which meant that they were intended to be the toughest camps for the "Incorrigible Political Enemies of the Reich".
Mauthausen never lost this Stufe III classification, the worst. In the offices of the RSHA (Reichssicherheitshauptamt) it was referred to by a nickname - Knochenmühle, the bone-grinder. Unlike many other concentration camps, intended for all categories of prisoners, Mauthausen was mostly used for extermination through labour of the intelligentsia, who were educated people and members of the higher social classes in countries subjugated by the Nazi regime during World War II.