Portrait of Don Whalen, probably a high school student in Boulder City, Nevada, holding a basketball.

Petroglyphs in the Boulder City Dry Fall Area. The exact location is unknown, but the location is possibly in Keyhole Canyon. Petroglyphs are pictogram and logogram images created by removing part of a rock surface by incising, picking, carving, or abrading. Outside North America, scholars often use terms such as "carving", "engraving", or other descriptions of the technique to refer to such images. Petroglyphs are found world-wide, and are often associated with prehistoric peoples. The word comes from the Greek words petro-, theme of the word "petra" meaning "stone", and glyphein meaning "to carve", and was originally coined in French as pétroglyphe. The term petroglyph should not be confused with petrograph, which is an image drawn or painted on a rock face. Both types of image belong to the wider and more general category of rock art or parietal art. Petroforms, or patterns and shapes made by many large rocks and boulders over the ground, are also quite different. Inukshuks are also uni