There are many places in the West where travelers in the past have left their names, initials, or messages. Signature Rock in Wyoming and Newspaper Rock in Utah are just two examples.
A third can be found on a rock formation in New Mexico that today is part of El Morro National Monument. On this sandstone bluff can be found inscriptions from Spanish and English travelers dating back to 1605.
Those carvings pictured above can be found at the point of El Morro (which translates to "the headland."). They include "old Spanish carvings as well as English carved by members of the 1868 Union Pacific Railroad survey," according to the National Park Service.
I think we should keep adding to these names, on a controlled basis of course, so the monument remains a living history and not a museum piece. I'd like to know what other folks think about that idea.
Here's an essay I wrote about it: http://www.myhandicapparking.com/Morro.html
Pioneer Register in Capitol Reef NP is another example of historic graffiti. Early settlers shot their names and dates into the smooth walls of the narrow canyon.
In the book Cities of Gold, the author (Douglas Preston) visits El Morro. Apparently at one point the park service removed all signatures from after a certain date. Unfortunately those included some pretty cool ones, one of which was supposedly William H. Bonney, AKA Billy the Kid.
There is a rock in Idaho, Register Rock, where travelers of the Oregon Trail left their signatures. It is near Massacre Rock State Park, on the Snake River. Beautiful spot to camp and learn some great history.