The Mittergars subcamp was set up in November 1944 at the latest for construction work in the vicinity of the bunker construction site. It consisted of 34 prisoner barracks surrounded by a double barbed wire fence and two watchtowers. Camp prisoners had to build the camp on behalf of the SS. The unheated barracks, which were only lined with straw, housed ten people at a time in a very small space. The approximately 350 male prisoners, most of whom were Jewish, suffered from malnutrition, cold and catastrophic hygienic conditions. Guarded by members of the Organization Todt, they had to perform hard labour in the construction of the adjacent railroad line. Others were used in a neighboring concrete factory and for clearing work.

In April 1945, the SS began to clear the camp. A unit of the 14th US Armored Division reached Mittergars at the end of the month and liberated the few prisoners still in the camp. On site, the soldiers discovered a mass grave containing at least 42 bodies of murdered concentration camp prisoners. They were buried together with another 21 victims on a hill south of Mittergars by representatives of the US military.

In 1956, the bodies were exhumed and transferred to the Dachau concentration camp cemetery of honor. After the war, the subcamp was completely demolished. Only the remains of the foundations are still visible today.