Contrary to popular opinion, poison oak and poison sumac are seldom found in Illinois.
Poison oak is most common in the western United States, although it is also found in eastern states. It rarely is found in midwestern states.
Poison sumac is much less common than poison ivy or poison oak. It is found in wooded, swampy areas, such as Florida and parts of other southeastern states. It is also found in wet, wooded areas in the northern United States.
According to Community Mental Health Board of Oak Park Township, here's where poison oak and poison sumac are not found:
None of these plants grow well above 4000 ft (1219 m), so the higher elevations in places such as the Rocky Mountains are relatively free of them.
None of these plants grow well in deserts, except along the banks of rivers, streams, and ponds. But heavy rainfall can make a dormant plant grow again, even in a desert.
Hawaii does not have any of these plants, although other plants that cause a skin rash are found on the islands. For example, mango trees grow in Hawaii, and the skin of mangoes contains the same allergenic oil (urushiol) as these plants.
These plants do not grow in Alaska, and they are rarely found in the rainforests of Washington state and Oregon.
Find out How to Get Rid of Poison Ivy, Poison Sumac, and Poison Oak at The Spruce.