The Mauthausen main camp operated from 8 August 1938, several months after the German annexation of Austria, to 5 May 1945, when it was liberated by the United States Army.

[7][note 1] Mauthausen initially served as a strictly-run prison camp for common criminals, prostitutes,[12] and other categories of "Incorrigible Law Offenders".

[16][17] At about that time, the construction of a new camp "for the Poles" began in Gusen (Langenstein) about 4.5 kilometres (2.8 mi) away after an order by the SS (Schutzstaffel) in December 1939.

The Gusen site was expanded to include the central depot of the SS, where various goods seized from occupied territories were sorted and then dispatched to Germany.

[25] In March 1944, the former SS depot was converted to a new subcamp named Gusen II, which served as an improvised concentration camp until the end of the war.

The subcamps were divided into several categories, depending on their main function: Produktionslager for factory workers, Baulager for construction, Aufräumlager for cleaning the rubble in Allied-bombed towns, and Kleinlager (small camps) where the inmates worked specifically for the SS.

[27] The list of companies using slave labour from Mauthausen and its subcamps was long, and included both national corporations and small, local firms and communities.

In January 1944, similar tunnels were also built beneath the village of Sankt Georgen by the inmates of Gusen II subcamp (code-named Bergkristall).

[34] In January 2015, a "panel of archaeologists, historians and other experts" ruled out the earlier claims of an Austrian filmmaker that a bunker underneath the camp was connected to the German nuclear weapon project.

[40][41] Until early 1940, the largest group of inmates consisted of German, Austrian and Czechoslovak socialists, communists, homosexuals, anarchists and people of Romani origin.

[citation needed] Other groups of people to be persecuted solely on religious grounds were the Sectarians, as they were dubbed by the Nazi regime, meaning Bible Students, or as they are called today, Jehovah's Witnesses.

The first groups were mostly composed of artists, scientists, Boy Scouts, teachers, and university professors,[7][42] who were arrested during Intelligenzaktion and the course of the AB Action.

[45] In early 1941, almost all the Poles and Spaniards, except for a small group of specialists working in the quarry's stone mill, were transferred from Mauthausen to Gusen.

Much like all the other large groups of prisoners that were transferred to Mauthausen and its subcamps, most of them either died as a result of the hard labour and poor conditions, or were deliberately killed.

[47] Throughout the years of World War II, the Mauthausen and its subcamps received new prisoners in smaller transports daily, mostly from other concentration camps in German-occupied Europe.

[50] Many more perished from exhaustion during death marches, or in railway wagons, where the prisoners were confined at sub-zero temperatures for several days before their arrival, without adequate food or water.

[59] Statistics showing the composition of juvenile inmates shortly before their liberation reveal the following major child/prisoner sub-groups: 5,809 foreign civilian labourers, 5,055 political prisoners, 3,654 Jews, and 330 Russian POWs.

"[65] The SS guards would often force prisoners – exhausted from hours of hard labour without sufficient food and water – to race up the stairs carrying blocks of stone.

[69] At times the guards or Kapos would either deliberately throw the prisoners on the 380-volt electric barbed wire fence,[69] or force them outside the boundaries of the camp and then shoot them on the pretence that they were attempting to escape.

While the prisoners were still beaten on a daily basis and the Muselmänner were still exterminated, from early 1943 on some of the factory workers were allowed to receive food parcels from their families (mostly Poles and Frenchmen).

Several Norwegian Waffen SS volunteers worked as guards or as instructors for prisoners from Nordic countries, according to senior researcher Terje Emberland at the Center for Studies of Holocaust and Religious Minorities.

The inmates unable to cope with the hard labour and malnutrition were exterminated in large numbers to free space for newly arrived evacuation transports from other camps, including most of the subcamps of Mauthausen located in eastern Austria.

The prisoners transferred to the "Hospital Subcamp" received one piece of bread per 20 inmates and roughly half a litre of weed soup a day.

[82] This made some of the prisoners, previously engaged in various types of resistance activity, begin to prepare plans to defend the camp in case of an SS attempt to exterminate all the remaining inmates.

The following day, the guards of Mauthausen were replaced with unarmed Volkssturm soldiers and an improvised unit formed of elderly police officers and firefighters evacuated from Vienna.

He attempted to create an International Prisoner Committee that would become a provisional governing body of the camp until it was liberated by one of the approaching armies, but he was openly accused of co-operation with the SS and the plan failed.

All work in the subcamps of Mauthausen stopped and the inmates focused on preparations for their liberation – or defence of the camps against a possible assault by the SS divisions concentrated in the area.

[88][89] He had managed to survive with the help of several prisoners and was later a key witness at the Mauthausen-Gusen camp trials carried out by the Dachau International Military Tribunal.

[3] A visitor centre was inaugurated in 2003, designed by the architects Herwig Mayer, Christoph Schwarz, and Karl Peyrer-Heimstätt, covering an area of 2,845 square metres (30,620 sq ft).

[94] The Mauthausen site remains largely intact, but much of what constituted the subcamps of Gusen I, II, and III is now covered by residential areas built after the war.