Haslach experienced its first heyday in the 13th century when the town, seat of the mountain judge, became the center of an important silver mining area.

Its market streets and squares, which were wide for the time, have been completely preserved to this day and, together with the narrow residential and craft alleys, give the picturesque old town, which consists almost exclusively of baroque half-timbered houses, a unique flair.

Oriented at the medieval town plan, the city then emerged relatively modern timber-framed buildings in southern German baroque style.

During the last months of World War II (September 1944–April 1945), Haslach had three sub-camps of the concentration camp Natzweiler-Struthof at the volcano near the city.

Reason for the establishment of the camp was the relocation of production of several arms factories in the bombproof tunnels of the mine Hartsteinwerke volcano.