Coke ovens converted coal into coke, a cleaner-burning fuel that produced little smoke and helped power the iron and steel industry in nearby Birmingham. Construction here began in the late 1880's, and by 1889 one hundred forty ovens were producing coke. The surviving end buttresses once held in place the insulating layer of earth covering the beehive coke ovens. The first two rows built, now referred to as rows two and three, each contained double ovens with ovens on each side of the row. By the summer of 1890, during Alabama's iron and steel boom, demand for coke rose sharply, and rows of single ovens were added on each side of the original rows, creating a total of four hundred sixty-seven ovens stretching along four rows. Made by charring coal much as charcoal is charred from wood, coke burned hotter than coal, was lighter to transport, and contained fewer impurities such as sulfur that could weaken steel.