Ghost Signs

"A ghost sign is an old hand-painted advertising signage that has been preserved on a building for an extended period of time. The signage may be kept for its nostalgic appeal, or simply indifference by the owner. Ghost signs are found across the world with the United States, the United Kingdom, France and Canada having many surviving examples. Ghost signs are also called fading ads and brickads. In many cases these are advertisements painted on brick that remained over time. Old painted advertisements are occasionally discovered upon demolition of later-built adjoining structures. Throughout rural areas, old barn advertisements continue to promote defunct brands and quaint roadside attractions."
Wikipedia
The Basement Geographer
Ghost Sign Project (Video)
Ghost signs: Jersey's commercial history is written large in faded paint on city buildings
Ghost Signs Part 1, Part 2
Portland's ghost signs
Ghost Signs
American Ghosts : About Ghost Signs
Ghostsigns
San Francisco Ghost Signs: A Tour of SF's Historical Advertisements
NYT: The Handwriting on the Wall Says, ‘GiGi Young Originals’