Mule haulage, cans on trucks
Two mules are shown harnessed to railed ore carts at an unidentified lead-zinc mine in Oklahoma. Miners stand near the mules. Oklahoma is part of the Tri-state mining district that was a major lead-zinc producer from the mid 1800s to the mid 1900s. Although district production started earlier, lead was first mined in Oklahoma in the 1890s. Both lead and zinc were produced in Oklahoma until 1967 when the last mine ceased production.