Our drive south took us through the Navajo reservation where we noticed these huge, old and peeling photographic murals on many of the delapidated and abandoned buildings. Turns out they're part of a street art project by Chip Thomas.
A doctor who has worked on the Navajo nation since 1987, Thomas taught himself black and white photography and did his first photo installation on the Navajo reservation in
Perhaps I haven't dug deeply enough yet, but in researching Thomas' project, I haven't been able to find anything in his words addressing the "why" of the project, other than the fact that he saw something similar by someone else somewhere else and liked it, but it seems fairly obvious that the imagery, especially its monumental size, speaks to Navajo pride and identity based on sheep herding as a lifestyle. From what I've read on his blog, he seems to be working pretty intuitively, not thinking a lot or pontificating a lot about why he's doing what he's doing, but it seems to work nicely, even at its most random.
For really edgy street art that is very consciously making political statements and pointed cultural critique, check out Banksy.