The Cottonmouth ('round here in Kentucky a.k.a. the 'Water Moccasin' or 'Cottonmouth Moccasin') can actually range up into parts of Southern to Central Illinois, Indiana and Ohio. These areas also have wetlands areas where these snakes prefer to nest.

By far the most predominate viper in this part of the country is the copperhead snake (both northern and southern varieties, according to this page: http://www.kentuckysnakes.org/). There are also Timber Rattlesnakes and Eastern Diamondback rattlers.