The Illinois gives you one lane and a lot of company in it. A loaded tow needs the width of the channel and most of the bend, and it cannot hand any of that back at short notice, so the passing arrangement gets made early or it gets made badly. The water under you is rarely what decides the day. What decides it is the height of whatever has been built across the river, and where the passage stops and waits for a chamber. Plan a day on this water by distance and you will be wrong by hours.
Helm builds a chart pack for the Illinois that runs from 38.94 N up to 41.85 N and from 90.67 W across to 87.61 W. Inside it are 307 bridges and 136 overhead cables, 948 charted lights, 201 charted depth areas and 273 depth contours, 24 charted lock features, 33 charted wrecks, 26 restricted areas, 8 underwater rocks and 3 charted obstructions. The whole pack downloads at 4 MB. At that size there is no reason to be selective about which end of the river you take with you.
Helm builds chart packs for fifteen US rivers. The Illinois places high in one family of figures and mid table in another, and the split is the useful part. What ranks here is what has been built across the river and what has been lit along it. Depth data sits ninth of fifteen on both counts, which is the ordinary shape of the numbers on water where the channel is a worked and re-worked thing rather than a surveyed seabed.
Read down that list and a corridor shows up. 307 bridges and 136 overhead cables on a single river is a density you never see on open water, and it is there because the banks are close together and a crossing is cheapest where a river is narrow. The same narrowness is why the lights count for so much. 948 of them, third of the fifteen, on water where you are never far from either side of it.
| In the chart pack | Count |
|---|---|
| Bridges | 307 |
| Overhead cables | 136 |
| Charted lights | 948 |
| Lock features | 24 |
| Charted depth areas | 201 |
| Depth contours | 273 |
| Charted obstructions | 3 |
| Charted wrecks | 33 |
| Restricted areas | 26 |
| Underwater rocks | 8 |
| Lateral buoys | 3 |
Counted from the Helm chart pack for the Illinois River, built from the official inland electronic navigational charts published for it. The pack downloads at about 4 MB. Lock features are counted as the chart draws them, with chambers, gates and dams as separate objects.
307 bridges and 136 overhead cables comes to 443 crossings on one river, and every one of them is a ceiling. The cables are the half to think about first. 136 of them puts the Illinois third of the fifteen rivers Helm packs, and a cable does not open and does not answer a radio call. It holds the height it was strung at, in the heat and in the cold, and the only negotiation available is the one you did at the dock.
This is the figure that decides whether the boat can make the trip at all. A sailboat with the stick up and a motoryacht with a flybridge, an arch and a radar mast are asking the same question of all 443, and they are asking it in a place where turning around is a maneuver rather than a decision. Set your air draft in Helm once and the charted vertical clearance on each crossing is checked against that figure, which is worth doing before the run and not at the second one that looks tight.
The pack carries 948 charted lights and 3 lateral buoys. Those two counts describe the same channel. Three is the highest lateral buoy count of the three rivers in Helm's set that carry any at all, which tells you what a floating lateral mark is worth on moving water that runs hard in the spring and freezes at the top end. The Illinois is marked from the bank and from fixed structures, and it is marked with light.
For a night run or an early departure that changes the job. You are not picking up a buoy and holding it. You are matching a light on the bank to a light on the chart and working out which of the two you can see belongs to the channel and which belongs to a dock. Helm draws all 948 where the chart puts them, so the one in front of you can be found on the screen before you commit the boat to it.
The pack carries 24 charted lock features, sixth of the thirteen rivers Helm packs that have any charted. That count treats a chamber, a gate and a dam as separate objects, so it is a description of charted geometry and not a count of the places you will stop. Among the sites drawn in it are Brandon Road, Marseilles, Starved Rock and LaGrange.
A lock is the part of the passage you cannot plan your way around. A tow locking through ahead of you takes the time it takes, and one that has to be split takes considerably longer than that. Nothing on a chart tells you which of those you are about to sit behind.
What the chart does give you is the approach. Where the chamber sits, which bank the approach wall is on, where the dam line runs across the river from it. Knowing all of that before you come around the bend above it is most of what a chart can do for you here, and it is the difference between arriving set up and arriving sideways.
201 charted depth areas and 273 depth contours put the Illinois ninth of fifteen on both. That is the expected shape of the data on a working channel. The chart describes the water as it was surveyed, and the channel itself answers to the last high water and to whatever came down the river with it. When a depth comes from the chart rather than from a survey of the channel's current state, Helm says which one it is using, and on a river that distinction is the one worth having.
Then the fixed things. 33 charted wrecks, fifth of the fifteen, 8 underwater rocks and 3 charted obstructions. Only six of the rivers Helm packs carry any underwater rock at all, and the Illinois is fifth of those six, so geology is not what is going to hurt you here. Sunken hulls are a different matter. 33 wrecks on water where the channel is the only place to be is a different proposition from 33 wrecks spread across a bay you can cross anywhere.
There are also 26 restricted areas in the pack, seventh of the fourteen rivers that have any, which is the count a waterway produces when it has terminals and federal structures along its whole length. They are drawn on the chart so you can see the edge of one from outside it.
These counts describe what the chart pack carries, not the state of the river today. Charted data ages, pools change with the dams, and a lock can be out of service. Keep a lookout, listen to the traffic, and verify locally.
The pack carries 307 bridges and 136 overhead cables, which is 443 crossings on one river, and Helm checks the charted vertical clearance on each of them against the air draft you set. The cables deserve the first look, because a cable holds the height it was strung at and has no tender to call. 136 of them puts the Illinois third among the fifteen US rivers Helm builds packs for.
Yes. The pack carries 24 charted lock features, sixth of the thirteen rivers Helm packs that have any charted. That figure counts chambers, gates and dams as separate charted objects, so it describes the geometry rather than the number of places you stop. Brandon Road, Marseilles, Starved Rock and LaGrange are among the sites in it, drawn with their approaches and the dam line across the river.
The pack runs from 38.94 N up to 41.85 N and from 90.67 W across to 87.61 W, and it comes down as a single 4 MB file with all 307 bridges, 136 overhead cables, 948 charted lights and 24 charted lock features in it. The Upper Mississippi River and the Ohio River are separate packs, so a trip that carries on past either end of the Illinois means one more download before you leave the dock.
Helm Boating