This post is long over due and I apologize as I promised this topic a while ago. Petroglyphs are prehistoric, created by Native Americans, at least the ones in the USA. They are etchings in rock that have endured for thousands of years. Most can be found throughout the west, especially the southwest. Others, though fewer, can be found in other parts of the country as well. The meanings of the art are usually uncertain. We can makes some assumptions about some, glean information from others, but much remain open to speculation. A fascinating aspect of petroglyphs is their relation to astrology. On certain dates and times, the sun, moon, or stars light up particular petroglyphs for added significance. Some of the panels we have seen indicate times for planting and for harvest. Some of the speculation concerns possible alien contact. The subject around this ancient art is fascinating. Depending on the location, some petroglyphs have been determined to have been created by different tribes in different time periods. Then there is the issue of vandalism from much more modern times.
The joy of discovery, the hunt, is probably what we most enjoy about petroglyphs. Our first finds were not something we set out to look for, but once started, we kept our eyes and ears open. When we began hunting, we relied on vague directions from people in an area. We would be told that there were glyphs on a particular road, but usually not anything more precise than that. With the internet, you can gather so much more data and see what you are looking for before you set out o your hunt.
Petroglyphs are found on rocks (hence the name.) But you can be standing, and often are, in front of a huge mountain of rock, hundreds of feet high trying to find something that is difficult to find. Glyphs can be easy to see, at eye level, but many can be difficult to find. One clue is to look for a flat section of rock, often with "varnish." Varnish is the black stuff that naturally occurs on the rock and the etching stands out better against the black background. The shapes and images are quite varied. Some seem to tell stories and others seem quite random. Keep in mind as you discover glyphs that the images are of things that the native peoples would have had experience with. You will be hard pressed to find a crocodile or elephant glyph in Idaho, so be realistic when considering the shapes you see.
When you do discover some petroglyphs, please respect the historic nature of them. DO NOT TOUCH THEM! It should go without saying that you should not add your own etching or graffiti or disturb the site in any way. Back home, make your own family glyph and, who knows, it might survive for thousands of years too.