Located at the point where the Allegheny and Monongahela Rivers join to form the Ohio, Pittsburgh rapidly grew into a major industrial center in the 19th century.

The bustling city became famous for existing under a perpetual haze of coal smoke. As early as 1807, residents were discussing what could be done to address the black dust filling the air and coating buildings.

The smoke control movement was hampered by numerous myths and misconceptions about smoke. Many believed smokiness was indicative of high productivity, or even that smoke was good for the lungs or aided crop growth.

After the end of World War II, the movement gained steam, led by the United Smoke Council. A grassroots campaign for smoke control legislation aimed to curb the emissions of coal-burning trains, factories and homes.

The movement was a success. Clean air legislation was enacted, freeing the city from its smoky miasma. Pittsburgh was soon touted around the world as an environmental success story.