Donora is an old industrial town located in a region south of Pittsburgh known as the "Mon Valley." Many of the towns in this area, due to the loss of industry and suburbanization, have suffered population decline for decades. Donora has an interesting and tragic history. In 1948, air pollution from local steel plants became trapped in the town. Within days, 20 people had died. This event was known as the Donora Smog of 1948. Although intact, the main business district of Donora is largely vacant.