By the time of the Civil War, there were small coal mines along the riverbanks near Carbon. In 1894, there were nine coal mines in Carbon, of which five were then in use. Typical mine shafts were 80 feet deep, working a coal seam 12 to 20 inches (30 to 50 cm) thick. The town at that time was described as a mining camp. Unlike the vast majority of Iowa's coal camps, the UMWA had no union local in Carbon between 1900 and 1912; during that period, most of Iowa's coal camps were organized, and the largest UMWA locals in the country were based in Buxton and Centerville, Iowa.