Discovering Unrecognized Lead-Smelting Sites by Historical ...
Apparently, "hundreds" of plants were in the business from 1941 to 1942.15,16 In 1969, 150 firms were reported to be in business.18 By 1994, the number of firms had declined to fewer than 20 and the number of plants to fewer than 30.6,14,18 Discovering Unrecognized Lead-Smelting Sites by Historical Methods