Illinois
Snakes in Williamson County
18 species have been documented here, 3 of them venomous.
Venomous snakes in Williamson County
Full guide & what to do if bitten →
Eastern CopperheadAgkistrodon contortrixVenomousHeavy body, triangular head, vertical pupils, and a heat-sensing pit between each eye and nostril.
Northern CottonmouthAgkistrodon piscivorusVenomousHeavy body, triangular head, vertical pupils, and a heat-sensing pit between each eye and nostril.
Timber RattlesnakeCrotalus horridusVenomousHeavy body, broad triangular head, vertical (cat-like) pupils, and a segmented keratin rattle at the tail tip.
Every snake recorded in Williamson County
Common Watersnake
Nerodia sipedon
Harmless
Gray Ratsnake
Pantherophis spiloides
Harmless
Eastern Copperhead
Agkistrodon contortrix
Venomous
Common Garter Snake
Thamnophis sirtalis
Harmless
Prairie Kingsnake
Lampropeltis calligaster
Harmless
Rough Greensnake
Opheodrys aestivus
Harmless
Diamondback Watersnake
Nerodia rhombifer
Harmless
Eastern Milksnake
Lampropeltis triangulum
Harmless
DeKay's Brownsnake
Storeria dekayi
Harmless
North American Racer
Coluber constrictor
Harmless
Plain-bellied Watersnake
Nerodia erythrogaster
Harmless
Eastern Hognose Snake
Heterodon platirhinos
Harmless
Black Kingsnake
Lampropeltis nigra
Harmless
Northern Cottonmouth
Agkistrodon piscivorus
Venomous
Red-bellied Snake
Storeria occipitomaculata
Harmless
Timber Rattlesnake
Crotalus horridus
Venomous
Common Wormsnake
Carphophis amoenus
Harmless
Smooth Earthsnake
Virginia valeriae
Harmless
Compiled from verified GBIF & iNaturalist observations. Informational only.