credit: Smoke Control Lantern Slide Collection, ca. 1940-1950, AIS.1978.22, Archives Service Center, University of Pittsburgh.
The University of Pittsburgh writes:
For more than a century, Pittsburgh was marked as a smoky city. The earliest recorded discussion of smoke control in Pittsburgh dates from 1807, with periodic resurges in interest.
After the Civil War, Anthony Trollope, the noted British novelist, wrote, "Pittsburgh without exception is the blackest place which I ever saw, the site is picturesque, even the filth and wondrous blackness are picturesque.... I was never more in love with smoke and dirt than when I stood and watched the darkness of night close in upon the floating soot which hovered over the city."