Western Diamondback Rattlesnakes, or Crotalus atrox, measure 3 to 5 feet long and can grow up to 7 feet. Known to be one of the largest rattlesnakes in the western U.S., these reptiles are quite scary! Even with their heavy bodies and diamond-backed patterns, their dark cheek stripes are quite noticeable. Most commonly found in Arizona, Arkansas, California, Oklahoma, Texas, and New Mexico, these rattlesnakes are quite a sight and are most often seen around dry mountain areas and prairies, as well as rocky canyon tourist zones.