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North Star Tannery, Mercersburg, Franklin County, PA, 1878.
Credit: J.F. Richard, History of Franklin County. Chicago: Warner, Beers, 1887.
"Tanning" is a process that prevents decomposition of the animal skin, by treating it with tannin, an acidic chemical compound found in the bark of hemlock and certain other trees. Tanneries created such foul odors that they were almost always banished to the very furthest outskirts of any town.