Beginning in 1911, the Crucible Coal Company developed Greene County's second largest mine along the Monongahela River south of Rices Landing, using coal from the Pittsburgh seam for shipment to Midland to be made into coke for the company's steel mill. The company bought about 2,000 acres from J.V. Thompson and associates in February 1911, announced plans that spring for two shafts, an air shaft, a large tipple, 150 steel barges, and 100 miner houses, and also acquired the surface acreage of three farms, the Arensburg ferry, and a new steam ferry to move construction materials across the river from Fayette County. Work on the shafts, tipple, and a new road to the hilltop mining town began in August, and by November the number two shaft was finished and the first coal was taken. By 1913, 166 men worked there and 120,126 tons of coal had been removed. Production reached its highest levels in the late 1920s, when about one million tons were produced annually and employment averaged more than 800 miners. During the Depression, production fell to 368,000 tons and 336 miners in 1932, though the mine stayed open while others closed and sometimes operated only a few days each week amid job-sharing efforts. Demand rose again with World War II and the postwar building boom, and Crucible again produced more than one million tons and employed more than 800 miners, but mechanization steadily reduced employment over the next twenty years. After 1957 production dropped sharply, and it stopped in October 1961 because the mine could no longer competitively produce the quality coking coal needed for the steel company's specialty steels. From 1913 to 1961, Crucible Mine produced more than 36.5 million tons of coal from the Pittsburgh seam. After the Crucible Coal Company closed the mine, Pittsburgh Coal Company maintained it and it was later conveyed to National Mines Corporation; a tunnel under the Monongahela River connected it with the Isabella Mine in Fayette County, and coal continued to be removed from Crucible reserves until the Isabella Mine closed in 1984. Before World War II, coal from deep mines was loaded into cars on tracks and brought out by several methods, including mine mules, which were valued for the donkey's sure feet and endurance combined with the horse's size, strength, and temperament. In 1913, mules cost about $200, could begin work at age 3, and lived to 30. Often stabled underground to save time, they lived in stalls with feed and straw and rarely went outside except for a blacksmith, veterinarian, or mine shutdown. Miners often visited them during lunch or while coming and going from work. Electric locomotives, mechanization, and conveyors gradually replaced mules, and animal welfare and safety regulations in the 1960s and 70s ended their use in U.S. mines.