The Mauthausen camp was established shortly after Germany annexed Austria in 1938. Located near the city of Linz, the object was to quarry granite for the massive Nazi building projects in Germany, using forced labor. In 1939, the camp and quarry were extended to nearby Gusen. In the ensuing years, additional sub-camps in Austria were set up to provide slave labor for other industries supporting the war, resulting eventually in some 101 subordinate locations. The conditions were intentionally harsh, as the camp was designated as Grade III -- imprisoning "incorrigible political enemies of the Reich." This translated to "extermination through labor" of the intelligentsia of subjugated countries as well as many socialists, communists, anarchists, homosexuals, and people of Romani origin. It is estimated at least 150,000 died; perhaps double that number. As the Allied armies approached, the SS was ordered to evacuate or execute the remaining prisoners. Attempts to seal them in underground tunnels failed. They set up a death march on May 1st, but it was aborted. The SS fled on May 3rd, turning the camp over to local unarmed police, who in turn surrendered the camp to US Army units on May 5th. In the entire camp system, only about 80,000 survived.  Link. Map