Pittsburgh Botanic Garden is built on land that was once actively mined for coal. This industrial use, and the ensuing abandonment of the land, created a hazardous landscape that had to be remediated before the site could be opened to the public.
Starting in the 1920s, the area was mined through “room and pillar” mining, a common practice at the time, whereby tunnels were excavated to reach a coal seam. Coal was removed, leaving “pillars” of coal to support the layers of rock above. Overlying layers of rock could collapse into the mines at any time, even after the mine was abandoned.