America’s Working Waterways: Post VI- The Middle Mississippi — Where the Locks End

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Where the Locks End

Back when it was still called ADM Growmark we ran a grain dock in St. Louis right across from Lock 27. It had twin loading towers, and on a normal day the river did most of the work for us. Empties were pulled up on a cable and winch system, then let down on the current under the spouts and on down the dock once they were loaded. No boat needed. Just steel cable, a good tower operator, and a river that was behaving.

The river didn’t always behave. Depending on the stage, the current at the dock would set the other way, and we had to turn the whole operation around and work barges against it. It didn’t happen often, but it happened enough that everybody on that dock knew when it happened and what to do.

Winter and spring brought their own problems. That dock sat where ice came down from both the Upper Mississippi and the Missouri, and every spring the Missouri sent down heavy drift, whole trees, root balls, and anything else the river picked up on the way. A loaded barge is a big target for a cottonwood with the current behind it.

Our answer was a kicker barge. Usually it was an old steel rolltop, set at an angle off the upstream bank so it would throw the ice and drift out into the channel and away from the dock.

We learned why we needed it the hard way. One spring, before the kicker was in place, a load of drift hit the upper barge tower and knocked a barge loose. It went downriver on its own and hit the bridge just below the dock before a harbor boat could catch it. They got hold of it before it reached the next bridge.

The dock still runs today under the ADM name. The river still runs the same way it did then, too. Locks and dams manage the river above that spot. Below it, the Mississippi runs open to the Gulf, and you work with whatever it hands you. That stretch, from the Missouri down to Cairo, is the Middle Mississippi, and it’s the hinge the whole river system turns on.

The Corridor

The Corps of Engineers defines the Middle Mississippi as the stretch between the mouth of the Missouri and the mouth of the Ohio. Their St. Louis District puts it at 195 miles. If you’ve been reading this series from the start, Post III covered the Mississippi as a whole. This post zooms in on the piece in the middle that most people drive over without thinking about.

It starts with rock. Just north of St. Louis, the river runs over what rivermen have always called the Chain of Rocks, a 17-mile run of rock ledges that made low-water navigation dangerous for as long as anybody ran boats there. Proposals to cut a canal around it go back to 1904. The Corps finally built one after World War II.

The Chain of Rocks Canal is 8.4 miles long and runs down the Illinois side. Lock 27 sits near the bottom end of it, near Granite City, at river mile 185.5. It opened on February 7, 1953, with a main chamber 110 by 1,200 feet and an auxiliary chamber 110 by 600 feet. Lock 27 and Mel Price, about 17 miles north of St. Louis, are the two 1,200-foot locks a tow passes on its way into St. Louis harbor.

Lock 27 is the last lock on the Mississippi. It is the only one below the Missouri confluence, and it moves more cargo in a year than any other single structure on the river. Below it, there are no more locks between St. Louis and the Gulf.

So how does the Corps hold a 9-foot channel on 195 miles of open river? Not with dams. The authorized channel is 9 feet deep and at least 300 feet wide, with extra width in the bends. The Corps holds it with what it calls the Regulating Works Project, which goes back to Rivers and Harbors Acts in 1910, 1927, and 1930. Revetments hold the banks in place. Dikes and other river training structures push the current into the channel so the river scours its own bed. Dredging fills in where the structures can’t keep up. Rock removal takes care of the bedrock that shows up in droughts.

Then there’s the Missouri. It comes in carrying a big sediment load, and the Mid Miss has to move all of it. Anybody who has stood on the riverfront at St. Louis knows the water below the confluence doesn’t look like the water above it. That mud is a big part of why dredges stay busy on this stretch. The stretch ends at Cairo, where the Ohio joins and the open river continues as the Lower Mississippi. The dynamics of that junction—flows, backwater, and how the two rivers meet will be covered in the Ohio post.

How Grain Moves Through It

Everything above St. Louis is built around lock chambers. A tow coming down the Upper Miss or the Illinois is sized to fit them, and that usually means 15 barges. Once those barges clear Lock 27, the chambers stop setting the limit. The width and depth of the channel set it instead.

That’s why St. Louis harbor is where tows get rebuilt. Fleeting areas hold barges coming off the upper rivers. Harbor boats break up the 15-barge tows and build them into the bigger open-river tows that head south. In normal water, tows below St. Louis often run 30 to 40 barges, and some line-haul boats have pushed 42 or more. The mechanics of how that works are in the companion post, “How the System Actually Runs.” What matters here is that St. Louis is the one place where the whole system changes gears.

The winter job

Here’s something people outside the trade don’t always think about. Every winter, the upper river shuts down. Ice ends the season at St. Paul around the end of November, and the Corps uses the cold months to close locks for repair. In some years that has included Locks 24 and 25 just north of St. Louis, from mid-December to the end of March.

The Illinois, the Ohio, and the Mississippi from St. Louis south stay open through the winter, weather permitting. That makes the Illinois and the St. Louis area the northern end of open-water grain loading on the Mississippi for several months a year. Grain that would have gone on the water farther north either goes to rail, waits in the bin, or gets trucked down to a river terminal that can still load.

Winter on this stretch isn’t easy either. As the opening story showed, ice comes down from both the Upper Miss and the Missouri. The Corps put Lock 27 at the lower end of the canal, which means ice has to pass through the lock chamber in winter. In heavy ice years, the Coast Guard has cut tow sizes between St. Louis and Cairo to 15 or 16 barges.

Draft is money

Per series rule, here are the units. Post III used about 1,500 short tons per barge at the 9-foot Upper Miss draft, which is roughly 53,500 bushels of corn, and about 2,100 tons at the 12-foot draft barges can run on the Lower Miss. The Middle Mississippi is authorized for 9 feet, but in decent water the river runs deeper than that and barges load heavier for the run south. In 2012 a St. Louis barge line owner told NPR his barges had been carrying 2,200 tons from St. Louis to New Orleans before the drought cut them back. When the river drops, the barge companies cut draft, and every foot of draft lost is a lot of bushels left on the bank.

Who Loads It

Like the Illinois post, I’m going to group this by reach instead of trying to list every elevator. Ownership on the river changes more than people think, and I’d rather send you to the right reach than hand you a list that’s out of date by spring.

St. Louis harbor reach (spotlight)

This is where most of the action is. The harbor runs on both banks, Missouri and Illinois, and it handles grain that comes in by water from the upper rivers, by rail from all over the Corn Belt, and by truck from the farms around it. The stretch is sometimes called the Ag Coast of America because of the concentration of high-capacity barge-loading facilities in a short distance.

The dock in the opening story is a good example of how this harbor has changed hands over the years. ADM and Growmark once put their grain marketing and river terminals together, and terminals on the Illinois and Mississippi carried the ADM/Growmark name. Growmark says that venture was dissolved in 2007. The dock across from Lock 27 runs under the ADM name today.

A newer example sits on the Illinois side at Cahokia. COFCO International built a grain terminal there around 2017 that takes rail and truck grain and loads it into barges. Growmark bought a small stake in it shortly after, then sold that stake back to COFCO in June 2024 as part of an asset swap that gave Growmark the B-House grain warehouse in Chicago. Two southern Illinois congressmen asked for a federal review of the Chinese ownership. As of January 31, 2026, CHS Inc. operates the terminal under a lease from COFCO. The facility has track for up to four unit trains at a time and has two high-speed barge loading towers.

Other major operators in the St. Louis harbor area include Cargill, Bunge, Consolidated Grain & Barge, Louis Dreyfus, Bruce Oakley, and additional ADM and SCF facilities on both banks. Many of them take unit trains. The exact roster changes; the constant is that this is the system’s main rebuild and transfer point.

Chester and the Kaskaskia mouth

The Kaskaskia comes in just above Chester. Post V covered the Kaskaskia and its port district, so I won’t repeat it here.

Cape Girardeau and Scott City

Semo Port, the Southeast Missouri Regional Port Authority, sits near Scott City, 48 miles above the Ohio. It was created in 1975, the slackwater harbor opened in 1990, and its own switching railroad started in 1994. It connects to Union Pacific and BNSF, so it’s a true barge, rail, and truck transfer point. Consolidated Grain and Barge operates a grain elevator there that loads barges at roughly 40,000 bushels an hour. First Missouri Terminals and related entities also handle grain and other dry bulk. Semo Port is a working multi-modal facility for grain as well as fertilizer and other commodities.

What Goes Wrong

The kicker barge and those occasional reversals at our dock were the river’s constraints showing up at the bank. Here’s what they look like across the whole 195 miles.

Rock

The Chain of Rocks isn’t the only rock on this stretch. There are limestone pinnacles in the riverbed near Thebes, roughly river miles 46 to 38, and a shorter reach near Grand Tower, around miles 80 to 79. In normal water they sit under sand and plenty of river. In a drought, they don’t.

The first contract to blast them out was done in 1988 and 1989, taking advantage of that low water. The drought of 2012 brought them back. In December 2012 the Corps put contractors to work on about six miles of river near Thebes, with the Coast Guard holding traffic for part of each day. Rain in January 2013 bailed everybody out before the job was finished. The Corps came back with a second phase in December 2013, when the water dropped again. In low water, bigger tows that can’t get through have to break up and take the reach in pieces.

Low water

The record low on the St. Louis gauge is minus 6.2 feet, set in January 1940. The recent droughts haven’t beaten it, but they didn’t need to. During 2022 the St. Louis gauge bottomed out at minus 3.53 feet on December 25. That fall, barge companies capped tows south of St. Louis at 25 barges, when 30 to 40 is normal. USDA’s Grain Transportation Report showed the barge rate out of St. Louis hitting $105.85 a ton for the week ending October 11, 2022. A year later, in late August 2023, the St. Louis rate was running 42 percent over the same week in 2022.

That’s the whole story in one number. When the gauge drops, the freight goes up, and the basis goes with it.

High water

The St. Louis record crest is 49.58 feet, on August 1, 1993. The Weather Service says navigation on both the Mississippi and Missouri had been shut since early July of that year. In 2019, the river crested at 46.02 feet, the highest since 1993, and stayed above flood stage long enough to break the 1993 record for consecutive days.

When the St. Louis gauge goes over 38 feet, traffic through the harbor stops. Even after the harbor reopened in 2019, tows between St. Louis and Cairo were held to five barges and daylight only for a time. Lock 27 had two weeks that spring with no grain moving through it at all. Year-to-date grain through Lock 27 was running 67 percent below the three-year average by late June.

Spring rises on the Missouri bring the drift, too. That’s what knocked our barge loose.

Ice

Ice is mostly a winter nuisance on this stretch, but some winters it’s more than that. In heavy ice years the Coast Guard has held northbound tows between Cairo and St. Louis to 15 barges and southbound to 16. The railroad bridge at Thebes has taken hits from tows in ice and high water.

One lock at the top

Lock 27 has two chambers, but they aren’t equal. When the 1,200-foot main chamber is down, every 15-barge tow has to go through the 600-foot auxiliary in two pieces. The lockmaster told the Waterways Journal a few years ago that it takes about twice as long. The Corps closed the main chamber from January 1 to April 1, 2025, for repairs on the lock walls, scheduled for the slow season on purpose. Everything coming off the Upper Miss and the Illinois has to pass this one structure to reach the open river.

The training structure fight

The dikes and weirs that hold the channel have critics. In May 2020, five conservation groups sued the Corps in the Southern District of Illinois. They argued the structures raise flood heights along the Middle Mississippi and wanted the Corps to redo its environmental review. The district court granted summary judgment to the Corps in January 2022; the Seventh Circuit affirmed in 2023. The Corps prevailed. Anybody shipping off this stretch should know the case existed, because what happens with training structures decides how the Corps holds the channel.

Real Alternatives

On the Illinois, when a lock goes down, you can at least see the problem and put a date on the fix. On the Mid Miss, the failures come from the weather and the riverbed. Nobody can schedule a rain. So when this stretch gets tight, the only real alternative is to move grain on land.

• Rail. St. Louis harbor terminals take a lot of grain by rail already. The Cahokia terminal, for one, has track for up to four unit trains at a time. When the river is tight, more grain goes straight to the Gulf or the PNW by rail instead of transloading.

• Processors. Corn and soybean plants in Illinois and Missouri compete for the same bushels the river terminals want. When barge freight spikes, the processor bid starts looking a lot better.

• Truck to another terminal. Grain that can’t load at one dock can sometimes be trucked to another one with better water. That works for a short haul. It doesn’t work for a whole harvest.

• Hold it. Sometimes the answer is to store it and wait for the river. That’s where your bin space plan earns its keep.

Competition doesn’t make the river less important. It makes reliability more important.

What Needs to Change

Keep Lock 27 working. It’s 1953 concrete carrying more cargo than any other structure on the river. Scheduled closures in the slow season, like the 2025 main chamber job, are the right way to do it. The alternative is finding out in the middle of harvest.

Get ahead of low water. In 2022, most of the dredging was reactive. In 2023 it was more proactive, according to ACBL. That’s the direction to keep going. Stage dredges before the river drops, and finish the rock work at Thebes and Grand Tower before the next drought, not during it.

Fund the Regulating Works Project steadily. This stretch is held open by dikes, revetments, and dredges, not dams. That work only holds if it’s maintained year after year.

Settle the training structure question. The courts have ruled. Shippers and river towns still need a clear, durable answer on how the Corps will hold this channel for the next 20 years.

Watch the right numbers. If you market grain anywhere above Cairo, watch the St. Louis gauge and the St. Louis barge rate in USDA’s weekly Grain Transportation Report. When either one moves, it shows up in your river bid.

The Mid Miss is the hinge of the whole system. Every bushel loaded on the Illinois or the Upper Miss has to get through this stretch to reach the Gulf. What those rivers can ship depends on what this one will carry.

Operator’s Scorecard: Middle Mississippi

Measure	Middle Mississippi
Length	195 miles, Missouri River mouth to Ohio River mouth (USACE St. Louis District)
Primary commodities	Grain and oilseeds down; fertilizer, coal, aggregates, petroleum, chemicals, and other bulk
Channel depth	9 feet deep, at least 300 feet wide, held by training structures, revetments, dredging, and rock removal
Locks	1: Lock 27, 110 × 1,200 main and 110 × 600 auxiliary, at the foot of the Chain of Rocks Canal; open river below
Typical tow	30 to 40 barges below St. Louis in normal water; cut to 25 or fewer in low water
Main loading areas	St. Louis harbor (both banks—Cargill, Bunge, CGB, Louis Dreyfus, ADM, CHS/COFCO Cahokia, Bruce Oakley, and others), Chester area, Cape Girardeau/Scott City (Semo Port, including CGB)
Seasonal risk	Late summer and fall low water; spring and summer high water; winter ice and spring drift
Modal alternatives	Rail to Gulf and PNW, Illinois and Missouri processors, truck to other terminals, storage
Strategic vulnerability	Rock at Thebes and Grand Tower in low water; Lock 27 as the single gate to the open river; harbor shutdown above 38 feet at St. Louis

GG50 Operator Take

The Mid Miss doesn’t get much attention because there’s no big lock project to argue over. But when the St. Louis gauge drops, every elevator from Peoria to the Quad Cities feels it in the bid. I spent enough years fighting that river from a dock across from Lock 27 to know it doesn’t care about your loading schedule. You don’t manage the Middle Mississippi. You keep up with it.

What’s your experience been with this stretch? If you’ve loaded off the St. Louis harbor or fought a low-water fall below it, tell me about it in the comments. Next up in the series is the Ohio.

Thank you for reading and for being part of this conversation. Whether you work at an elevator, a processor, a terminal, or simply care about how grain gets from field to market, the fundamentals are worth reviewing. Your feedback helps shape this blog, so please share your experience and perspective.

Link to Glossary: https://www.grainguyfifty.com/post/the-gg50-america-s-working-waterway-vocabulary-glossary-of-terms

Regards,

Grain Guy Fifty

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