• The Mississippi: A Visual Biography by Quinta Scott

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The Grand Chain


Chain of Rocks Bridge

Chain of Rocks Bridge

Two projects came together on the Chain of Rocks Bridge. I first this eccentric bridge in the 1960s on a return trip from Peoria, Illinois. My father, always intent on broadening my horizons, drove my across this bridge at the northern edge of St. Louis. I returned to it many times before it was closed in the 1980s.

I began learning the history of the bridge in the 1980s when I was working on Route 66, The Highway and its People, Photographs by Quinta Scott; Text by Susan Croce Kelly. I told the story of the bridge in Along Route 66, the Architecture of American’s Highway:

“In 1929 John R. Scott and Tom J. Scott, brothers, completed four miles of roadway from Mitchell to the east bank of the Mississippi where they had constructed a most eccentric toll bridge. It was narrow, only twenty feet wide. It had a right turn in the middle, and a remarkable view of the Chain of Rocks, a major obstruction to shipping in the Mississippi, and of the little castles which housed the pumps for the St. Louis waterworks.

 The Scott brothers and a group of investors began planning the Chain of Rocks bridge in 1924, two years before U.S. 66 was designated. They wanted to provide a way into St. Louis that by-passed Granite City, Madison, and Venice and cut eight to ten miles off the trip between Chicago and St. Louis. A bridge at the northern extreme of St. Louis would do that.

They started construction on the Missouri side before they had found the bedrock anchor for the pier on the Illinois bank. They never did, at least not in the place they needed it for a straight bridge. So, the Scott’s engineers poked around along the Illinois shore until they found bedrock 200 yards up stream, and built a 22 degree left/right turn into the bridge.

When the Scotts opened the bridge on July 20, 1929, Missouri and Illinois failed to mark it on their official maps. After the initial publicity, traffic dwindled and so did income from tolls. The bridge went into foreclosure. The Scotts reorganized, laid an additional 600 feet of road from the west end of the bridge to connect with Lindbergh Boulevard which became the 66 by-pass around St. Louis, and renewed their efforts to encourage drivers to use the bridge. Discouraged, they sold the bridge to the City of Madison, Illinois in 1939 which turned it into a “Golden Goose” until the Interstate-270 bridge replaced the narrow, two lane bridge with the right angle in the middle where two trucks, going in opposite directions, could not pass.”

I pretty much ignored the Chain, when writing The Mississippi: a Visual Biography, due out this year, but a came back to it when I began writing the Riverlands tour for TwoTankTours.com. 



Castles at the Foot of the Grand Chain

Castles at the Foot of the Grand Chain

It’s quite a story. The chain of rocks I talk about in the caption to the photograph of the bridge in Along Route 66, is not a rapids, it’s a low water dam. The Grand Chain as an Army Engineer termed it in 1871, is a ledge of limestone that stretches upriver for three miles from the little castles that sit in the river just below the bridge and above the dam.

“About a mile below the foot of Wilson’s Island is a ledge of rock, called the Grand Chain, extending apparently two-thirds across the river from the Missouri shore toward Cabaret Island, and entirely covered during ordinary stages of water, the main channel passing over the outer edge of the ledge, which is the lowest. Here a large stone dike has been constructed by the City of St. Louis, at a cost of $92,000, for the purpose of deflecting the water through Cabaret Slough. The effect has not equaled the expectations. The slough is rapidly filling up.”—Report of the Chief of Engineers, 1871

The Grand Chain, a series of rock ledges that impeded navigation, begins at the little castles in the river and stretches for three miles upstream. Illinoian ice blocked the channel of the Mississippi where it flowed to the east of the Grand Chain and forced the river to cut a new channel over erosion-resistant rock. Fingers of limestone reach out from the Missouri shore, creating the Grand Chain, a stone ledge that made navigation difficult at all river stages and impossible at low water. At this point glacial ice never touched the Missouri side of the river, though south of here the river flowed through the City of St. Louis and straight down Kingshighway. When the ice retreated the river continued to flow over the ledge of rock, but not along Kingshighway.

The Corps of Engineers decided to build a canal around the Grand Chain before the beginning of World War II. The war halted the project, which was resumed after the war. The Corps completed dredging the 8.4-mile long and 300-foot wide canal in 1953. The locks at the foot of the canal include a 1,200-foot main lock chamber and a 600-foot auxiliary chamber, which allow barges to pass to the main navigation channel.

The engineers dumped tons of rock to form the Chain of Rocks Low Water Dam. Work started in 1959 and was completed five years later. The dam is essentially a rock dike that stretches 3,240 feet from bank to bank, with a kink in the middle. Its average height is 8 feet LWRP, that is the elevation of the surface of the river at a low flow of 54,000 cubic feet per second. The crown of the dam is 30 feet wide. From the Illinois shore we see it as a rapids just below the Chain of Rocks bridge. 

The designers figured that the river would be higher and flow faster than LWRP 97% of the time annually. Completion of the low water dam rendered the river from here north to the north entrance of the Chain of Rocks Canal impassable. The engineers notched the dam with a 680-foot spillway a 3 feet LWRP.  By 1969 a narrow, shallow, but defined channel had begun to form downstream of the notch.


Confluence Greenway and Trail Net have gone a long way to restoring the Old Chain of Rocks Bridge and the wetlands and islands that surround its Illinois approach.

Flooded Wetlands south of the Chain of Rocks Bridge

Flooded Wetlands south of the Chain of Rocks Bridge

When the river goes down, if it ever goes down, I will post an image of the Low Water Dam that I always thought was the Grand Chain. 






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