In the 1970s and 80s, two guys set out to alter billboards with obscure images they made themselves. Their names? Larry Sultan and Mike Mandel. Their images often had no meaning, but were meant to mock advertising. They could be considered pioneers of street art. The duo published a book titled ‘Evidence’. It’s one of the most influential books on the subject of the use of found images.

“Beginning in 1973 and up until 1989, we worked together on open ended, allusive designs for outdoor advertising billboards, under the name Clatworthy Colorvues. The billboards were exhibited mostly in the San Francisco Bay Area, where we lived, but sometimes installed in other parts of the country, the result of workshops we led with graduate students, or exhibitions on appropriation and public art. With the billboard, we wanted to reach a larger and more varied public than would ever find its way into an art institution.”