Near Silver Bay in Lake County, Minnesota — The American Midwest (Upper Plains)
Fog Signal
— Split Rock Lighthouse —
Sound When Sight Fails
When bad weather obscured a lighthouse beacon, navigators relied on its fog signal. Swirling snow and pea-soup fog could even make Split Rock Lighthouse invisible during the day. Navigators aboard ore boats relied on the fog signal to determine their location.
What's That Noise?
The fog signal had a unique characteristic, or sound. A two-second blast of sound was followed by 18 seconds of silence. The signal was incredibly loud—about 120 decibels, on par with an ambulance siren. People could hear the signal in Beaver Bay, four miles away.
Inside the Building
The fog signal building housed two Franklin tandem air compressor engines connected to air tanks, which were in turn connected to roof-mounted sirens. To activate the fog signal, keepers powered up the engines, forcing air into the compressor tanks and out through the sirens. The original gas-powered engines were replaced with diesel models in 1932.
Left: Fog Signal Building, circa 1911. Middle: Frank Johnson, circa 1946. Right: Fog Signal Equipment, circa 1911. MNHS collections.
Erected by Minnesota Historical Society.
Topics. This historical marker is listed in these topic lists: Communications • Waterways & Vessels. A significant historical year for this entry is 1932.
Location. 47° 12.019′ N, 91° 22.026′ W. Marker is near Silver Bay, Minnesota, in Lake County. Marker can be reached from Split Rock Lighthouse Road, half a mile south of North Shore Scenic Drive (State Highway 61). Located at the Split Rock Lighthouse Historic Site. Touch for map. Marker is at or near this postal address: 3713 Split Rock Lighthouse Rd, Two Harbors MN 55616, United States of America. Touch for directions.
Other nearby markers. At least 8 other markers are within walking distance of this marker. Lighthouse (a few steps from this marker); Home Away From Home (a few steps from this marker); Oil House (a few steps from this marker); Storage Barn (a few steps from this marker); Steam Engine Hoist (within shouting distance of this marker); The Gales of November (within shouting distance of this marker); Geology of the Split Rock Region (within shouting distance of this marker); Anchor of the Madeira (about 300 feet away, measured in a direct line). Touch for a list and map of all markers in Silver Bay.
Also see . . . Split Rock Lighthouse. (Submitted on August 13, 2022.)
Credits. This page was last revised on August 14, 2022. It was originally submitted on August 13, 2022. This page has been viewed 135 times since then and 22 times this year. Photos: 1, 2, 3. submitted on August 13, 2022.