It is my understanding that, given the severe shortage of supplies, the Confederate army used bat guano to procure potassium nitrate (saltpetre), before mixing it with charcoal and sulphur, to create gunpowder. However, I cannot find anything that explains how they procured sulphur, given that sulphur mining did not occur in the South until after the Civil War ended (e.g. from Calcasieu Parish, Louisiana). Did they have external supplies, say from South America (which has sulphur rich volcanoes), or did they source sulphur earlier from somewhere more local somehow?