Missouri has five venomous snakes. The Copperhead, Timber Rattlesnake, Cottonmouth Moccasin, Western Pygmy Rattlesnake and Massasauga Rattlesnake. The Copperhead, Timber Rattler and Cottonmouth are by far the most common and could be found pretty much statewide so keeping an eye out is probably just a good idea. If you are working outside around brushy areas Missouri raises some record size ticks and chiggers and Lyme Disease is no joke so Permanone tick spray is an easy way to stay itch free. My wife has a bad case of poison ivy right now, watch out for "leaves of three." Enjoy your time in Missouri, be safe.