Two Harbors: Split Rock Lighthouseby Marc Sanchez, Minnesota Public Radio
Two Harbors, Minn. — Split Rock Lighthouse is easing into its century status. It began operating in 1910 and was celebrated throughout 2010 to mark its 100th anniversary.
The site was placed on the National Register of Historic Places in 1969, the same year it was decommissioned as a working lighthouse. The Minnesota Historical Society runs the facility, which is now part of a larger state park, where you will find meticulous recreations of what life was like at the lighthouse when it was in service.
Historical interpreters dressed in 1920's garb answer questions about the fog horn, the giant Fresnel lens, and the restored keeper's home.
The fog horn wasn't only for ships. Lee Radzak, historic site manager, says deer hunters would use the blasts to find their way out of the woods.
One of the most distinct sounds at Split Rock comes from high in the lighthouse tower, where the Fresnel lens (the "s" is silent in Fresnel) is wound. The lens is actually two pieces of thick, ribbed glass that slowly spin and project prisms up to 20 miles across Lake Superior. Two convex pieces of glass top a giant, threaded spool attached to a series of counter-weights, which slowly get lowered to turn the lens.
To keep the spool turning, the lighthouse keeper has to hand-crank the weights back up every two hours. The crank is inserted into a case that holds a series of cogs, similar to a grandfather clock. To ensure the lens rotated through the night, lighthouse keepers split overnight shifts among the three of them, who lived there.