Plains Indian biographic rock art can be “read” by those knowledgeable in its lexicon. Presented is a lexicon of imagery, conventions, and symbols used by Plains Indians to communicate their warfare and social narratives. The reader is introduced to Plains Indian “warrior” art in all media, biographic art as picture writing is explained, and the lexicon is described, providing a pictographic “dictionary,” and explains conventions and connotations. Finally, it illustrates four key examples of how these narratives are read by the observer. Familiarity with the lexicon will enable interested scholars and laypersons to understand what are otherwise enigmatic rock art drawings found from Calgary, Alberta through ten U.S. states, and into the Mexican state of Coahuila.