Illinois
Snakes in Cook County
20 species have been documented here, 2 of them venomous.
Venomous snakes in Cook County
Full guide & what to do if bitten →
Eastern MassasaugaSistrurus catenatusVenomousStout, dark-blotched body, nine large scales on the crown, and a small rattle.
Northern CottonmouthAgkistrodon piscivorusVenomousHeavy body, triangular head, vertical pupils, and a heat-sensing pit between each eye and nostril.
Every snake recorded in Cook County
Common Garter Snake
Thamnophis sirtalis
Harmless
Plains Garter Snake
Thamnophis radix
Harmless
DeKay's Brownsnake
Storeria dekayi
Harmless
Common Watersnake
Nerodia sipedon
Harmless
Eastern Foxsnake
Pantherophis vulpinus
Harmless
Smooth Greensnake
Opheodrys vernalis
Harmless
Red-bellied Snake
Storeria occipitomaculata
Harmless
Eastern Milksnake
Lampropeltis triangulum
Harmless
Queensnake
Regina septemvittata
Harmless
Graham's Crawfish Snake
Regina grahamii
Harmless
North American Racer
Coluber constrictor
Harmless
Western Ribbon Snake
Thamnophis proximus
Harmless
Eastern Massasauga
Sistrurus catenatus
Venomous
Kirtland's Snake
Clonophis kirtlandii
Harmless
Common Ribbon Snake
Thamnophis saurita
Harmless
Ring-necked Snake
Diadophis punctatus
Harmless
Northern Cottonmouth
Agkistrodon piscivorus
Venomous
Rough Greensnake
Opheodrys aestivus
Harmless
Eastern Hognose Snake
Heterodon platirhinos
Harmless
Smooth Earthsnake
Virginia valeriae
Harmless
Compiled from verified GBIF & iNaturalist observations. Informational only.