Diving For Dams: Historic ‘Road Construction’ on the St. Croix River

Little-known structures shed light on a 19th-century engineering feat.




6 minute read

“Ruins of a Forgotten Highway” Program
6:30 to 7:30 p.m., Thursday, June 25
Stillwater Public Library
Jessica Keller and Jean Schaeppi-Anderson will discuss the history of these 19th century water control structures and their 21st century remains. Details…

At the end of the nineteenth century, the St. Croix River was being used by more and more steamboats to carry crops from farmers in the region to distant markets, and to import other goods. At least, the steamboats were trying to do that. At the same time, logging of the region’s pine was hitting its peak and massive log jams, miles long, could block passage. Dams built by logging companies made for periods of either very low water or floods filled with lumber. The river was no longer the reliable highway it had been for millennia.

Finally, Congress ordered the Army Corps of Engineers to deal with the problem, and the agency embarked on an ambitious effort to ensure a three-foot-deep channel at all times. In the 1870s and 1880s, steamboat captain Oscar Knapp of Osceola and a crew of 16 men were hired to build structures that would force the flow into a main channel which could reliably be used for shipping. The Corps did this on many rivers that flow into the Mississippi.

“Navigation has been rendered permanent where formerly uncertain and in other places been made practicable where before it was impossible,” the district engineer at St. Paul in charge of the St. Croix projects reported in 1887, thirteen years after the project began.

Based on old, recently-discovered records, as well as rangers stumbling across mysterious structures during low water, researchers from special divisions of the National Park Service are spending the month of June on and in the river. Their goal is to document the remains of this civil engineering project on the St. Croix.

“There is no historical record of where the structures were built,” says team lead Jessica Keller, from the Submerged Resources Center. “Reports to Congress would just say the general area and, for example, ‘1,000 feet of dam built.’” The reports didn’t say how many, what type, how big, or where they were placed. It may be that a map once existed of all the structures, but if it did, it has been lost to time.

So the Park Service archaeologists, equipped with SCUBA gear, sonar, and surveying tools, set out to see what remains in the river. So far, they have found more than 100 likely structures, and are closely examining several to find and map examples of different types of dams.

The archaeologists from the National Park Service’s Submerged Resources Center are experienced underwater detectives. They travel to national parks around the United States diving and documenting. Their work on the St. Croix River will help the Park Service preserve the sites and allow river users to learn about them. For the first time, on this project they were partnering with the NPS Midwest Archaeological Center.

Submarine sleuthing

One afternoon during the third week of the project, the researchers were inspecting an island in the village of Marine on St. Croix. Keller was in the river with a colleague, diving below the surface to discover the extent of a structure thought to have been built by Captain Knapp and his crew.

The pair submerged for a few minutes, mostly using their hands to feel for rocks and timbers (“archaeology by Braille,” they call it). All was quiet, just occasional bubbles rising to the surface. A great blue heron flew over. Then they surfaced, talked things over with each other and their support team, and went back under to continue working their way down the dam.

“This one has a lot of structure,” Keller popped up to say. Later, they reported curious smallmouth bass and a catfish that wouldn’t move out of the way.

Underwater research is careful, methodical work, but in a few hours they identified what was thought to be a major streambank stabilization structure. It was built of rock and timber, with several large logs jammed into the sand underwater. It was built to last. The logging companies never put as much work into their dams.

Working in the river requires skill and caution and a cool head. Flippers seemed to give the swimmers an advantage, but they were sometimes pushed around by a strong current, or subject to stepping into dropoffs, all of it with a great deal of timber and other impediments below.

After figuring out where the structure laid, they worked their way back up and down it, putting buoys and temporary posts at its upstream and downstream extent and one major turn, and laying down a measuring tape and high visibility line that would serve as a baseline for mapping the whole site. They also took GPS readings and photographed the underwater structure, which is especially important because most people will never be able to get a good look at the artifact.

A fleeting feat

The river between Franconia and Stillwater was the biggest problem area for commercial activity during the boom of European immigration, due to the broad valley and many islands and side channels. It was here that most of the channel work was done. Ultimately, at least three miles of structures were constructed in the area, constricting this wide, winding, and shallow part of the river to a faster and deeper channel.

Things were made more difficult by logging dams. At one point, there were 60 to 80 on the river and its tributaries. Logging companies used them to store water in reservoirs where they could gather logs, and then release the logs and water to rush to the mills downstream.

Captain Knapp and his crew were responsible for taming this river – if only temporarily.

Once the logging boom ended in the early twentieth century, and as steamboat traffic dwindled, most people forgot about the dams. Documents were lost. Experienced boaters knew to avoid certain spots dangerous to props, structures were possibly dissembled to make way for docks or a landings, and the river slowly found its own course again, gradually dismantling the dams.

Remains of the quay

“We’ve had lots more success than we anticipated,” Keller said.

Traveling up and down the river, the archaeologists first used side-scan sonar to detect possible structures, and found more than 100. Then they counted 30 confirmed dams, and at least 16 that were related to the shipping channel project. One rock wing dam near Franconia is at least 300 feet long.

The structures come in several different types. Wing dams point into the current to push it toward the middle; closing dams block a slough, forcing the water into the main channel; revetments buttress a bank against increased current. Some of them were made of rock and bundles of brush, including one they were surprised to find near Log House Landing.

This project was initiated by staff from the Saint Croix National Scenic Riverway. It was two Saint Croix rangers, Linda Krings and Dale Cox, who first saw the structures while kayaking one busy Fourth of July weekend. The park’s historian, Jean Schaeppi-Anderson, did some initial research, and then brought in Dan Ott, a graduate student in history and past park guide, to find out more about the Army Corps’ project. His research took him all the way to the National Archives.

Schaeppi-Anderson gave a presentation at the St. Croix River Association’s office a few months ago about the project up to that point. It’s available to watch here.

Future of the history

What will come from the research depends on the local Park Service. The study will help them understand what is there, and perhaps take steps to preserve it and share it with visitors.

The island behind the Marine General Store is today called “Crunchberry Island” by some locals. Another knows it as “Eel Island.” On historic maps, it was bigger, but the upstream point in particular has now eroded significantly. It could be that the structure built along its east side was meant to help preserve this popular island near a bustling community – and keep the channel three feet deep.

Details about the program on Thursday, June 25 in Stillwater are available here. Much more information about the research project is available on the Saint Croix National Scenic Riverway’s website.


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One response to “Diving For Dams: Historic ‘Road Construction’ on the St. Croix River”

  1. john aka captnemo Avatar

    What a great find, wish I could join in but it’s a bit of a drive from California 🙂


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Diving For Dams: Historic ‘Road Construction’ on the St. Croix River