Engineering the Falls

Eastman Tunnel Collapse

Excavating for dams and tailraces ate away at the stone, and William Eastman's disastrous tunnel project nearly destroyed the falls in 1869. The whirlpool off Nicollet Island took seven years to plug.


Fall Erosion

This is a diagram of the rock formations beneath the falls. Water wore away the soft sandstone beneath the limestone, and the limestone ledge periodically broke off. This continuous process of erosion caused the falls to move upriver over many years.


Bridge Square Light Tower

In 1883, a 250-foot-tall light mast was constructed in the heart of Bridge Square to promote electric street lighting as an alternative to gas lights. In 1894, the Minneapolis General Electric Company constructed a generating plant on the site of the old east side platform lumber mills to power the new electric street lights.

The pace of the erosion of St. Anthony Falls increased after lumbering and milling began. Logs floating downriver crashed against the limestone and broke it off in great chunks. To prevent further damage, the U.S. Army Corps of Engineers built a concrete dike under the river and placed a wooden apron over the ledge. The Corps later replaced that apron with the current concrete spillway. It protected the falls, but their natural beauty was forever transformed.

In 1878, William de la Barre, a young Vienna-born engineer, called on owner Cadwallader C. Washburn after the Washburn A Mill explosion with a flour dust collecting device that he said would prevent such accidents. Washburn hired him to oversee the rebuilding of the A Mill. He stayed on as engineer for the milling companies that controlled the use of the falls. By studying seasonal effects on the river and falls, he improved the water distribution system and increased the over-all output of waterpower nearly six times.

To maintain an even flow of water, mill owners urged the government to build dams and reservoirs at the headwaters of the Mississippi. Over the bitter protest of the Ojibwe, the U.S. Army Corps of Engineers built six dams to control waterpower and navigation on the Mississippi. Begun in 1880, the dams raised the level of the lakes, destroying Indian homes, burial grounds and wild rice beds.

De la Barre found ways to utilize surplus waterpower at the falls to generate hydroelectricity. A small plant on the west bank made history in 1882 as the country's first central hydroelectric power station. Although it furnished light to a few retail businesses for a short time, it soon closed.

In 1897 a lower dam and a hydroelectric plant were constructed to capture the drop of the rapids below the main falls. This and other plants provided power to the fast-growing streetcar system. In the 1950s, electric streetcars gave way to buses, and demand for hydroelectricity to run the city's transit systems came to an end. The sole remaining use of the waterpower of the falls is at the 1908 Hennepin Island Hydroelectric Plant, operated by Northern States Power Company.

With completion of the Upper Lock at St. Anthony Falls in 1963, commercial navigation became possible above Minneapolis. During construction of the lock, the US Army Corps of Engineers altered the entire west side of the falls, eliminating Upton Island and most of Spirit Island and cutting off access to waterpower. What remains of Spirit Island lies beneath the breakwater leading into the lock.