Auschwitz I (or "the Main Camp") was the original camp. This camp housed prisoners, was the location of medical experiments, and the site of Block 11 (a place of severe torture) and the Black Wall (a place of execution). At the entrance of Auschwitz, I stood the infamous sign that stated "Arbeit Macht Frei" ("work makes one free"). Auschwitz I also housed the Nazi staff that ran the entire camp complex.

Heinrich Himmler's Schutzstaffel (SS) took full control of the police and the concentration camps throughout Germany in 1934–35.[5] Himmler expanded the role of the camps to hold so-called "racially undesirable elements", such as Jews, Gypsies/Romanis/Sintis, Serbs, Poles, disabled people, and criminals.[6][7][8] The number of people in the camps, which had fallen to 7,500, grew again to 21,000 by the start of World War II[9] and peaked at 715,000 in January 1945.[10]