The productive silver districts in the United States (exclusive of Alaska and Hawaii) are shown on the accompanying map. Only those districts known or believed to have contained 100,000 troy ounces or more silver are shown. Three size categories, based on production and estimated reserves, are distinguished and indicated by size of symbols: districts containing 100,000 to 5 million ounces, those containing 5 million to 50 million ounces, and those containing more than 50 million ounces. Symbols show the approximate centers of the districts.
Some of the more prominent districts are identified by name on the map, and all are numbered to correspond to the index. Because a name established through common usage may not be the legal name of the mining district, several names are given in the index for some localities. The index, arranged alphabetically by States, includes a brief description of major geologic features for most districts. Both published and unpublished data were used, and at least one reference is given for each locality if reports on it have been published.
