After W. Eugene Smith quit LIFE magazine in 1954, he shot more than 11,000 photographs of Pittsburgh from 1955-1957 for a book celebrating the city’s bicentennial. Smith documented every corner of this vibrant industrial metropolis — the most comprehensive visual chronicle ever made of an American city in motion. This striking image captures a steelworker tending production of coke, a fuel used to make molten iron. As Smith explained in the 1959 Popular Photography Annual: “Coke … is made from bituminous coal in long, narrow ovens … with openings on top aligned with railroad tracks. Cars drop the exact amount of coal into the ovens and men … follow the cars, pushing stray coal into the holes, dancing back from the flames that shoot out until they can get the lids back into place.” Smith’s son Kevin wrote: “Channeling an Impressionist painting, this photo casts a mystical glow over a very gritty process. It is my favorite Smith image.”