Snakes in Illinois
Illinois has 33 snake species on record, each with at least 10 GBIF records in the state, and 2,780 licensed records in all. The most recorded are the common garter snake, the DeKay's brown snake and the northern cottonmouth. Four of them are venomous.
Rattlesnakes in Illinois
Rattlesnakes are a small part of the snake record here: two species with 1% of records between them. The most recorded is the eastern massasauga (21), ahead of the timber rattlesnake (20).
Copperheads and cottonmouths in Illinois
Copperheads and cottonmouths: two species are listed for Illinois, with 308 records (11% of the state's snake records). The most recorded is the northern cottonmouth (259), ahead of the eastern copperhead (49).
Observation records of the northern cottonmouth in Illinois run mostly March through October, peaking in October; most licensed records come from Union County, Johnson County and Jackson County. Most licensed records of the eastern copperhead in Illinois come from Union County, Jersey County and Jackson County.
Water snakes and swamp snakes in Illinois
Water snakes and swamp snakes: eight species are listed for Illinois, with 408 records (15% of the state's snake records). The most recorded is the northern water snake (243), ahead of the plain-bellied watersnake (72).
Observation records of the northern water snake in Illinois run mostly April through September, peaking in May; most licensed records come from DuPage County, Cook County and Will County. Observation records of the plain-bellied watersnake in Illinois run mostly March through October, peaking in October; most licensed records come from Union County, St. Clair County and Johnson County.
Garter snakes and ribbon snakes in Illinois
Garter snakes and ribbon snakes dominate the snake record of Illinois: four species and 26% of all records. The most recorded is the common garter snake (427), ahead of the plains garter snake (250).
Observation records of the common garter snake in Illinois run mostly March through September, peaking in May; most licensed records come from Lake County, Cook County and DuPage County. Observation records of the plains garter snake in Illinois run mostly March through September, peaking in April; most licensed records come from Cook County, Lake County and Will County. Most licensed records of the western ribbon snake in Illinois come from Union County, St. Clair County and Jackson County.
Rat snakes and corn snakes in Illinois
Rat snakes and corn snakes: two species are listed for Illinois, with 169 records (6% of the state's snake records). The most recorded is the eastern rat snake (86), ahead of the eastern fox snake (83).
Observation records of the eastern rat snake in Illinois run mostly April through October, peaking in May; most licensed records come from Union County, Peoria County and Johnson County. Observation records of the eastern fox snake in Illinois run mostly April through September, peaking in June; most licensed records come from Will County, DuPage County and Champaign County.
Kingsnakes and milksnakes in Illinois
Kingsnakes and milksnakes: three species are listed for Illinois, with 164 records (6% of the state's snake records). The most recorded is the prairie kingsnake (82), ahead of the eastern milksnake (59).
Most licensed records of the prairie kingsnake in Illinois come from Jersey County, Richland County and Sangamon County. Observation records of the eastern milksnake in Illinois run mostly April through October, peaking in June; most licensed records come from Cook County, Jersey County and Iroquois County.
Racers, whipsnakes and indigo snakes in Illinois
One species of this group is listed for Illinois: the eastern racer, with 129 records (5% of the state's snake records).
Observation records of the eastern racer in Illinois run mostly April through October, peaking in May; most licensed records come from Madison County, Union County and Richland County.
Gopher snakes, bullsnakes and pine snakes in Illinois
One species of this group is listed for Illinois: the gopher snake, with 26 records (0.9% of the state's snake records).
Hognose snakes in Illinois
Hognose snakes are a small part of the snake record here: two species with 2% of records between them. The most recorded is the eastern hog-nosed snake (60), ahead of the plains hog-nosed snake (1).
Most licensed records of the eastern hog-nosed snake in Illinois come from Richland County, St. Clair County and Wabash County.
Green snakes in Illinois
Green snakes: two species are listed for Illinois, with 112 records (4% of the state's snake records). The most recorded is the rough greensnake (58), ahead of the smooth green snake (54).
Observation records of the rough greensnake in Illinois run mostly May through October, peaking in October; most licensed records come from Union County, Macoupin County and Jackson County. Most licensed records of the smooth green snake in Illinois come from Will County, Cook County and McLean County.
Small woodland and burrowing snakes in Illinois
Small woodland and burrowing snakes: six species are listed for Illinois, with 557 records (20% of the state's snake records). The most recorded is the DeKay's brown snake (313), ahead of the ring-necked snake (87).
Observation records of the DeKay's brown snake in Illinois run mostly March through October, peaking in April; most licensed records come from Cook County, Jo Daviess County and Lake County. Observation records of the ring-necked snake in Illinois run mostly March through October, peaking in April; most licensed records come from Union County, Pike County and Calhoun County. Most licensed records of the eastern wormsnake in Illinois come from Jersey County, Randolph County and Pike County.
Where in Illinois are snakes recorded most?
Union County leads with 424 records (15%), followed by Cook County and Lake County; the top five counties hold 44% of the total. 90 of Illinois's 102 counties have at least one licensed snake record.
| # | County | Records | Share |
|---|---|---|---|
| 1 | Union County | 424 | 15.3% |
| 2 | Cook County | 280 | 10.1% |
| 3 | Lake County | 244 | 8.8% |
| 4 | Will County | 166 | 6.0% |
| 5 | Richland County | 119 | 4.3% |
| 6 | St. Clair County | 115 | 4.1% |
| 7 | DuPage County | 111 | 4.0% |
| 8 | Jackson County | 107 | 3.8% |
| 9 | Jersey County | 105 | 3.8% |
| 10 | Champaign County | 82 | 2.9% |
| 11 | Madison County | 79 | 2.8% |
| 12 | Johnson County | 68 | 2.4% |
When do snakes come out in Illinois?
Observation records of snakes in Illinois run mostly April through October, peaking in October with 20% of them. December through February together hold under 2% of the records, so snakes in Illinois are rarely recorded in winter. The sharpest rise comes from March to April.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 0% | 0% | 8% | 18% | 19% | 13% | 5% | 6% | 10% | 20% | 1% | 0% |
Snakes: Illinois compared with its neighbors
Illinois ranks 16th of 50 states by the number of snake species listed; Texas leads with 86 species.
Of the five states bordering Illinois, Missouri lists more snake species (Illinois: 33 species; Missouri 36, Indiana 27, Kentucky 24, Iowa 22, Wisconsin 16).
What snakes are in Illinois? All 33 species
Ranked by licensed records in Illinois. Species with a profile page are linked.
| # | Species | Family | Records | Share |
|---|---|---|---|---|
| 1 | Common garter snake Thamnophis sirtalis | Colubridae | 427 | 15.4% |
| 2 | DeKay's brown snake Storeria dekayi | Colubridae | 313 | 11.3% |
| 3 | Northern cottonmouth venomous Agkistrodon piscivorus | Viperidae | 259 | 9.3% |
| 4 | Plains garter snake Thamnophis radix | Colubridae | 250 | 9.0% |
| 5 | Northern water snake Nerodia sipedon | Colubridae | 243 | 8.7% |
| 6 | Eastern racer Coluber constrictor | Colubridae | 129 | 4.6% |
| 7 | Ring-necked snake Diadophis punctatus | Colubridae | 87 | 3.1% |
| 8 | Eastern rat snake Pantherophis alleghaniensis | Colubridae | 86 | 3.1% |
| 9 | Eastern wormsnake Carphophis amoenus | Colubridae | 85 | 3.1% |
| 10 | Eastern fox snake Pantherophis vulpinus | Colubridae | 83 | 3.0% |
| 11 | Prairie kingsnake Lampropeltis calligaster | Colubridae | 82 | 2.9% |
| 12 | Plain-bellied watersnake Nerodia erythrogaster | Colubridae | 72 | 2.6% |
| 13 | Eastern hog-nosed snake Heterodon platirhinos | Colubridae | 60 | 2.2% |
| 14 | Eastern milksnake Lampropeltis triangulum | Colubridae | 59 | 2.1% |
| 15 | Rough greensnake Opheodrys aestivus | Colubridae | 58 | 2.1% |
| 16 | Smooth green snake Opheodrys vernalis | Colubridae | 54 | 1.9% |
| 17 | Western ribbon snake Thamnophis proximus | Colubridae | 50 | 1.8% |
| 18 | Eastern copperhead venomous Agkistrodon contortrix | Viperidae | 49 | 1.8% |
| 19 | Red-bellied snake Storeria occipitomaculata | Colubridae | 42 | 1.5% |
| 20 | Diamondback water snake Nerodia rhombifer | Colubridae | 26 | 0.9% |
| 21 | Gopher snake Pituophis catenifer | Colubridae | 26 | 0.9% |
| 22 | Queen snake Regina septemvittata | Colubridae | 25 | 0.9% |
| 23 | Eastern black kingsnake Lampropeltis nigra | Colubridae | 23 | 0.8% |
| 24 | Eastern massasauga venomous Sistrurus catenatus | Viperidae | 21 | 0.8% |
| 25 | Timber rattlesnake venomous Crotalus horridus | Viperidae | 20 | 0.7% |
| 26 | Graham's crayfish snake Regina grahamii | Colubridae | 19 | 0.7% |
| 27 | Smooth earth snake Virginia valeriae | Colubridae | 19 | 0.7% |
| 28 | Kirtland's snake Clonophis kirtlandii | Colubridae | 11 | 0.4% |
| 29 | Western worm snake Carphophis vermis | Colubridae | 11 | 0.4% |
| 30 | Mud snake Farancia abacura | Colubridae | 8 | 0.3% |
| 31 | Green water snake Nerodia cyclopion | Colubridae | 4 | 0.1% |
| 32 | Eastern ribbonsnake Thamnophis saurita | Colubridae | 1 | 0.0% |
| 33 | Plains hog-nosed snake Heterodon nasicus | Colubridae | 1 | 0.0% |
Also recorded in Illinois, fewer than 10 times
Beyond the main list, six snake species are known from Illinois by only 3 to 9 records each. Some are genuine rarities at the edge of their range; others may be strays, released pets or old misidentifications, so treat them as unconfirmed.
Related pages
GBIF records read 2026-09-29. Listed: any license. Counted: CC0/CC BY only. How we count.