I just got hold of a bunch of old Horizon Magazines - a bi-monthly hard cover magazine that was published by American Heritage from 1958 to 1989. Some of the issues from the 70s are brilliant. The images above come from an article in Summer 1976 titled "And Now, the Edifying Edifice: Fine Art Comes To The Side Of A Barn".
"People had been painting on barns long before the admen at Mail Pouch started using barn sides as billboards. But it was not until 1971 that anyone though of decorating barns not for commerce but art. The man who did it is an engaging twenty six year old artist named Douglas Tyler....He has now done seven barns, all of them in farm country near Detroit, and has three more waiting. Tyler's calling has its problems. The owner of the Mona Lisa Barn withdrew permission mid-smile, another burnt down. Worst of all, Tyler hates working on ladders."