Superior, Wyoming began in the coal boom around the turn of the century after a prospecting team led by Morgan Griffiths entered Horse Thief Canyon in 1900 and established the site of the first of Superior’s many coal mines. The town reached its largest population of 2,700 in the mid 1940s, when during World War II hundreds of workers came to the mines and lived in quarters made from boxcars. In their prime, the Superior mines produced nearly 24,000,000 tons of coal annually, second only to Rock Springs. Eight mines operated in the area, all but two owned by the Union Pacific Coal Company to supply its locomotives, while the Premier and Copenhagen Mines were independent. The Union Pacific mines were the last to close because they were forbidden by law to sell coal to the public and had little use for it after the coming of the diesel locomotive; the D.O. Clark Mine closed in 1963. South Superior was an incorporated town separate from the company town of Superior, and its hall and the buildings north of here remain as remnants of an independent venture that served miners after the company-owned houses and stores disappeared.