The Rapidan Dam is significant as a notable MInnesota example of the hollow reinforced concrete dams constructed by the Amburson Hydraulic Construction Company of Boston, Massachusetts. it is one of the early hydroelectric components of the power system that developed into Northern States Power Company, and was an important early source of electric power for Mankato and for southern Minnesota. The structure utilized the weight of the water to work with the weight of the structure rather than against it, was quicker to construct, less expensive, and more immune to ice damage than solid gravity dams.
Construction was begun in February and completed by December 1910. Local materials and labor were utilized to build it. The first power was generated on March 11, 1911, and with an intial capacity of 1500 kilowatts, the power produced at the dam more than doubled the capacity of Mankato's electric system. Mankato sorely needed this boost in power to move ahead as a manufacturing center in southern Minnesota. In the following years, power was supplied to many communities in the area and fed into lines that spread across southern Minnesota. Built by the Billesby Company, which went under the name Consumers Power Company in Minnesota, it was reorganized in 1916 into Northern States Power (NSP).
The spring flood of 1965 destroyed seven gates and production of electricity was discontinued. In 1966 NSP presented the dam and deed to adjoining land to Blue Earth County. In 1985 the dam was renovated and it again produced electricity. It is still producing electricity today.
A "dam moment" was August 1, 1949, when a 40-ton, 65-foot-high grain elevator was moved eight miles to Rapidan. To cross the Blue Earth River bridge on the dam, it had to be jacked up to a height of seven feet to clear the railing of the narrow, one-way bridge. Thousands of people came to watch and pictures of the elevator on the dam appeared across the state.
Rapidan Dam played an important role in the production of electricity for southern Minnesota, providing it to small communities and rural areas that otherwise would have had to wait decades for the "wonder of electricity."
~Jane Tarjeson, Good Thunder, MN