Herding cattle from horseback has been a tradition in northern Mexico and the American West since the Spanish colonial era. The first mounted herders were the Mexican vaqueros, expert horsemen who developed the skills to work cattle in the brush country and deserts of the Southwestern borderlands. From them, Texas cowboys learned the trade, evolving their own unique culture that spread across the Southwest and Great Plains. The buckaroos of the Great Basin west of the Rockies trace their origin to the vaqueros, with influence along the way from the cowboys, though they, too, have ways and...