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Man Standing by Generators in Power House, Prairie du Sac, Wisconsin, ca.1915.. WHS Image ID 48686

Man Standing by Generators in Power House, Prairie du Sac, Wisconsin, ca.1915. WHI 48686

From Water to Power: the Prairie du Sac Dam

The Prairie du Sac Dam on the Wisconsin River has been powering communities in the area since 1914. The idea of constructing a hydroelectric power plant to harness the power of the river came from Norwegian immigrant, engineer and inventor, Magnus Swenson. Although it took a little more than a decade for the dam to prove profitable, Swenson was ultimately proved to be correct and the surrounding areas of Sauk and Columbia counties have benefited from the dam's electric power production as well as the creation of Lake Wisconsin behind the dam.

Magnus Swenson formed the Southern Wisconsin Power Company with attorneys E.J.B. Schubring and Phillip L. Spooner to study the hydroelectric potential of the Wisconsin River in 1905. The success of the power plant at Niagara Falls, opened in 1896, had made many investors and utilities across the country and across Wisconsin look seriously at rivers as potential sources for hydroelectric power. Based on the findings, Swenson's company built a dam and power plant at Kilbourn, now Wisconsin Dells, on the Wisconsin River in 1909. But the relatively low demand for electricity and the high cost of construction made the dam, at first, unprofitable.

Swenson, however, remained convinced of the river's economic potential and he acquired another dam site north of Prairie du Sac. While the site presented a construction challenge due to its sandy soil, a dam there could produce three times the power of the Kilbourn dam so plans called for the use of thousands of timber pilings to secure the plant to the riverbed.

Construction began in 1911. The railroad was extended to transport materials to the site and a construction camp was built on the west bank of the river. Flooding in 1911 and 1912 and an ice break up in 1913 damaged the construction site, but despite these setbacks the power plant began production in September 1914.

Demand for power remained minimal beyond existing contracts with Madison Gas and Electric and The Milwaukee Electric Railway and Light Company, though, and Swenson was forced to sell both the Kilbourn and Prairie du Sac dams in 1916. The dam changed hands again in 1917, but under new ownership and incorporated as the Wisconsin Power and Light Company, the business began profitably selling electricity over high-voltage transmission lines in south-central Wisconsin.

The dam and power plant's construction was documented by local photographer Frank S. Eberhart, who operated a jewelry store and watch repair shop in town. His glass-plate negatives were found in his store building and were donated to the Society by former power plant superintendent Denman Kramer in 2007.

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