History
It was set up in the summer of 1940 as a satellite camp to Sachsenhausen, and became an independent camp on May 1, 1941. Initially, work was carried out in the camp's huge stone quarry, owned by the SS-Deutsche Erd- und Steinwerke GmbH. As the complex grew, many inmates were put to work in the construction of the subcamps' facilities.
Gross-Rosen was known for its brutal treatment of NN (Nacht und Nebel) prisoners, especially in the stone quarry. The brutal treatment of the political end Jewish prisoners was not only due to the SS and criminal prisoners, but to a lesser extent also due to German civilians working in the stone quarry. In 1942 for political prisoners the mean survival time was less than 2 months. Due to a change of policy in August 1942 the prisoners should survive longer because they were needed as slave workers in German industries. Therefore, some prisoners who were not able to work and not yet dying within a few days, were sent to Dachau in so-called invalid transports. One of these, Willem Lodewijk Harthoorn, an inmate from the end of April to mid-August 1942 wrote an account of his experiences, Verboden te sterven (in Dutch, meaning Forbidden to Die). The largest population of inmates, however, were Jews, initially from the Dachau and Sachsenhausen camps, and later from Buchenwald. During the camp's existence, the Jewish inmate population came mainly from Poland and Hungary; others were from Belgium, France, Greece, Yugoslavia, Slovakia, and Italy.
At its peak activity in 1944, the Gross-Rosen complex had up to sixty subcamps located in eastern Germany and occupied Poland. In its final stage, the population of the Gross-Rosen camps accounted for 11% of the total inmates in  concentration camps at that time. A total of 125,000 inmates of various nationalities passed through the complex during its existence, of whom an estimated 40,000 died on site and in evacuation transports. The camp was liberated on February 14, 1945, by the Red Army.
*source: wikipedia.org