Jo Daviess County. Our own 3DEP reading at the USGS point is 1,234 feet. The low point is 279 feet where the Ohio joins the Mississippi at Cairo, a Corps of Engineers figure in the USGS table
Against under 32 inches in the north. Snow runs the other way, 36 inches a year up north and under 10 in the far south
Tires for wet clay, not for rock
Nothing in Illinois needs a 35-inch mud terrain, and plenty of it punishes one. The pavement is excellent, the gravel is fine, and the failure mode is a greasy clay surface after rain in the southern hills. An all-terrain with real siping and a compound that stays soft in the cold does more good here than an aggressive tread that loads up and skates.
Two legal points. Studs are prohibited on Illinois highways except for rural letter carriers and certain disability plate holders in winter, and tread below 3/32 of an inch may not be sold or leased for highway use. Chains are allowed but never required, because the state publishes no traction law at all.
Tires are the only part of the vehicle that touches the ground, and on a loaded rig they work close to their limits. A good tire shop starts with load rating and size, then tread. It will also tell you when the tire you want will rub, need different wheels or throw off your gearing.
Expect help with
01Choosing a tire by load, terrain and season
02Wheels with the right offset and load rating
03Mounting, balancing and tire pressure sensors
04A matching full-size spare
05Alignment, rotation and repairs
How to choose tires for overland travel
Tread pattern is the last decision, not the first.
01Match the load rating to your real axle weights, not to the badge on the fender.
02All-terrain tires suit most overland travel. Mud-terrains are louder, heavier and wear faster, and earn it only in real mud and rock.
03Buy five. A matching full-size spare that you rotate in is worth the money when the nearest tire shop is a day away.
04Check the wheels too. Wheels have load ratings, and the wrong offset stresses bearings and rubs.
05Ask whether the shop can move or reprogram your tire pressure sensors.
What to have ready before you ask for a quote
A tire quote is quick when the shop knows what the tire has to carry.
01Vehicle, current tire size and wheel size
02Lift height, if any
03Loaded weight, or a list of what is on the vehicle
04Where you drive most: pavement, gravel, rock, sand, snow
05A budget range for five tires
Questions people ask
What does load range mean?
It describes how much weight a tire can carry at a given pressure. Heavier builds, vans and truck campers usually need a higher load range than the vehicle came with. The tire's sidewall and the placard in the door jamb are the places to start, and a tire shop can work through the numbers with you.
How big can I go?
Every platform has a size that fits at stock height, a size that fits with a modest lift, and a size that needs trimming and gears. Tell the shop your lift and wheels and ask what fits without rubbing at full steering lock and full compression.
Should I air down?
On washboard, sand and rock, lower pressure gives a better ride and more traction and is easier on the vehicle. It also means you need a way to air back up before pavement. How low depends on your tire, your weight and your speed, so ask your tire shop and start conservatively.
How high is Illinois?
From Cairo at 313 feet to Charles Mound at 1,235.
Altitude decides what your engine, your brakes and your lungs have to work with, and how late in the year the passes open.
02,000
Feet above sea level
Towns
ShelbyvilleShelby County seat at Lake Shelbyville, six federal campgrounds and two state parks on one reservoir, with Hidden Springs State Forest ten miles southeast.646 ft
JonesboroUnion County seat. Mississippi Bluffs Ranger District office, Trail of Tears State Forest five miles northwest, and the LaRue Pine Hills loop starts here.570 ft
OquawkaHenderson County seat on the Mississippi. Big River State Forest and its 60 miles of firebreaks are eight miles north on the Oquawka to Keithsburg road.553 ft
WilmingtonOn State Route 53, the old Route 66 alignment, two miles south of the Midewin National Tallgrass Prairie headquarters and welcome centre.543 ft
Forest CityMason County village that is the headquarters address for Sand Ridge State Forest, the largest state forest in Illinois and its main backcountry camping.494 ft
BentonFranklin County seat off I-57. Rend Lake and its five public campgrounds sit west of town, with the Corps office on Rend City Road.473 ft
CarlyleOn US 50 fifty miles east of St. Louis at the largest lake in the state, with the Corps visitor centre on the shore and camping all round it.460 ft
MurphysboroJackson County seat on Route 149. Johnson Creek Recreation Area on Kinkaid Lake, one of four Shawnee campgrounds rated for a 40-foot rig, is northwest.419 ft
CarbondaleLargest town in southern Illinois and the working base for the western Shawnee. Giant City State Park is near town and the Mississippi Bluffs district office is south at Jonesboro.416 ft
ViennaJohnson County seat on Route 45. Hidden Springs Ranger District office, one of the forest’s two districts and the office that issues its own motor vehicle use map.412 ft
Carrier MillsAddress of the Sahara Woods site office and the nearest town to the only state-run off-highway vehicle trails in Illinois.395 ft
HarrisburgSaline County seat on US 45. Shawnee National Forest supervisor’s office is on Highway 145 south of town, the Garden of the Gods road leaves Route 145 for Route 34, and the state OHV park is five miles west.394 ft
Cave-in-RockOhio River village at the state park with the 55-foot cave. The free Cave-In-Rock Ferry crosses to Kentucky here, supported jointly by both states.375 ft
ElizabethtownHardin County seat on the Ohio River Scenic Byway, between the Garden of the Gods road and the river, with Tower Rock’s free campground east on Route 146.361 ft
GolcondaPope County seat on the Ohio River Scenic Byway, on the eastern side of the Shawnee in the Hidden Springs district.354 ft
CairoThe southern tip of Illinois where the Ohio meets the Mississippi at 279 feet, the state low point, and where the Illinois stretch of the Ohio River Scenic Byway ends.313 ft
Passes, high roads and summits
Charles MoundThe highest point in Illinois, in Jo Daviess County in the far northwest corner. Our own 3DEP reading at the USGS point is 1,234 feet1,235 ft
Williams HillPope County, high ground in the Shawnee Hills on the eastern side of the national forest. The figure is our own reading of the elevation surface at its map point, because no agency publishes one1,062 ft
Bald KnobUnion County, in the hills behind the Mississippi bluffs on the western side of the national forest. The figure is our own reading of the elevation surface at its map point, because no agency publishes one1,028 ft
Pass, road and summit elevations are the figures published by the agency that manages them. Town elevations are the town’s or county’s own
figure where it publishes an exact one; the rest are from the U.S. Geological Survey (3D Elevation Program at the place’s official coordinates),
retrieved September 18, 2026. Every source is listed at the foot of the page.
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