Split Rock Light

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**Split Rock Light**
The tower of the Split Rock Lighthouse, Summer 2004
Location:	Silver Bay, Minnesota
Coordinates WGS-84 (GPS)	47.20005° N -91.3669° E
Foundation:	stone
Year first lit:	1910
Deactivated:	1969
Automated:	never
Tower shape:	Hexagonal
Height:	54 foot tower on a 130 foot cliff
Original lens:	3rd order, bi-valve type Fresnel lens
Range:	22 miles
Characteristic:	0.5-second flash every 9.5 seconds

Split Rock Light is a lighthouse located just south of Silver Bay, Minnesota, USA on the North Shore of Lake Superior. The structure was designed by lighthouse engineer Ralph Russell Tinkham and was completed in 1910 by the United States Lighthouse Service at a cost of $75,000, including the buildings and the land. It is built on a 130-foot (40 m) sheer cliff of anorthosite. The lighthouse was first lit on July 31, 1910. It was built in response to the loss of ships during the famous Mataafa Storm of 1905, in which 29 ships were lost on Lake Superior.

The tower of the lighthouse is hexagonal and constructed of brick, reinforced with a steel skeleton. It is topped with a steel lantern. The lighthouse features a large third order, bi-valve type Fresnel lens manufactured by Barbier, Bernard and Turenne Company in Paris, France. The lens floats on a bearing surface of liquid mercury. Originally, the lens was rotated by an elaborate clockwork mechanism that was powered by counterweights running down the center of the tower. When completed, the lighthouse was lighted with an incandescent oil vapor lamp that burned kerosene. In 1940, the station was electrified and the lamp was replaced with a 1000 watt electric bulb.

Split Rock was also outfitted with a fog signal housed in a building next to the light tower. The original signal was a pair of steam sirens driven by two Franklin 30-HP gasoline-driven air compressors manufactured by Chicago Pneumatic Tool Company. In 1932 the gasoline engines were replaced with diesel engines. The steam sirens were replaced with a a Type F diaphone (be-you) type signal in 1936. When the station was electrified four years later, the fog signal began to be powered by electricity. The fog signal was discontinued in 1961.

The light was retired in 1969 by the U. S. Coast Guard. The lighthouse is now part of the Split Rock Lighthouse State Park and is operated by the Minnesota Historical Society. The site includes the original tower and lens, the fog signal building, the oil house, and the three keepers' houses. It is restored to appear as it did in the late 1920s. The site was added to the National Register of Historic Places in 1969.