What Illinois asks of a build
Forget altitude. The towns in this guide run from 313 feet at Cairo to 646 at Shelbyville, and the state high point is 1,235. What Illinois tests is water, clay and salt. The state climatologist calls flooding the single most damaging weather hazard here, and the southern forest that holds the unpaved roads takes over 48 inches of rain a year against under 32 up north.
Decide early whether you are building one vehicle or two. A full-size truck is welcome on every forest road, byway and Corps campground in the state and is barred from the only motorised trail system, which admits nothing wider than 64 inches. If you want both, the second vehicle rides on a trailer, because the park requires it.