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
Suspension for gravel, ruts and a loaded tongue
Illinois driving is low speed on gravel and clay with weight on the back. Forest roads in the Shawnee and the fire lanes and gravel systems of the four state forests sit on soils that hold water, and the roads close or wash rather than get rough. Spring rate set for the load you actually carry beats long travel every time.
If you tow a machine to the state OHV park, say so when you spec the rear. A loaded trailer tongue on a truck already carrying a camper changes rear geometry and brake balance, and the 20 mph limit on state roads means you will be doing it slowly with a lot of steering input in tight gravel turns.
A suspension shop matches spring rates and shock valving to the vehicle's real loaded weight, corrects the geometry that a lift changes, and aligns it afterward. On an overland vehicle the goal is control and durability under constant load, not maximum height.
The work usually includes
01Coil and leaf springs rated for the load
02Shocks: monotube, remote reservoir or adjustable
03Control arms, track bars, driveline and brake line corrections
04Air bags or helper springs for heavy rear loads
05Alignment after the work
06Advice on gearing when tire size goes up
How to choose a suspension shop
The right shop asks about weight before it asks about height.
01Weigh the vehicle loaded, or ask the shop to. Choosing springs without a weight is a guess.
02Ask what else the lift changes on your platform: alignment range, driveline angles, brake lines, headlight aim and driver-assistance sensors.
03Ask whether they align in house.
04Ask for the least height that clears your tires and keeps the geometry happy. More lift is not better.
05Ask how it will ride at both ends of your use: empty around town and loaded on washboard.
What to have ready before you ask for a quote
Weight is the number that matters.
01Year, model and drivetrain
02Current tire size and the size you want to run
03Everything bolted on: bumper, winch, rack, tent, drawers, water
04Loaded weight, if you have been across a scale
05How you use it, and a budget range
Questions people ask
How much lift do I need?
Less than you think. Most overland travel is dirt roads, washboard and the occasional ledge, and the vehicle spends its life loaded. Enough lift to clear a sensible all-terrain tire, with springs rated for your weight, usually drives better and breaks less than a tall kit.
Why does my truck sag in the back?
Because the factory springs were chosen for an empty truck. Drawers, a fridge, water, a tent and a rear bumper add constant weight. The fix is springs rated for that constant load, sometimes with air bags for the occasional heavy trip.
Do bigger tires mean I need new gears?
Larger tires make the engine and transmission work harder and change the speedometer reading. Whether re-gearing is worth it depends on the tire size, the vehicle and how much weight you carry. A shop that knows your platform can tell you where the line is.
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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