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There was a time when you'd see barn advertisements for tourist sites like Rock City and Meramec Caverns, as well as for commercial products like Mail Pouch chewing tobacco, all over the American roadside. Over the years, this trend faded away for some reason. (And in part, because of the Ladybird Johnson's 1965 "Highway Beautification Act".) Now, instead of seeing these as advertisments, we look on them in hindsight as almost a form of folk art.
In the case of Rock City barns, a man named Clark Byers started painting them in 1935. When he retired in 1969, he had painted some 900 barns in 19 states. Fewer than 100 remain out that number, some still maintained by Rock City.