Sending a Signal

Dense fog on Lake Huron threatened vessels carrying passengers and valuable cargo, and when visibility was poor mariners relied on sound to navigate into the St. Clair River. Early fog signals were simple hand bells rung from shore. As traffic on the lake increased, a more reliable system was introduced in 1871 at Fort Gratiot with an eight-inch steam whistle installed north of the tower. A second unit was added south of the tower in 1881. In 1900, a new brick Fog Signal Building with a larger steam-powered diaphone replaced the two older whistles. An electric diaphone replaced the steam-powered system in the 1920's when the station was electrified. In the 1930's, an electric oscillating signal tower was added to the site, and in the 1970's the fog horn systems were removed and replaced with a fog horn on buoy #7 in Lake Huron.

Port Huron, Michigan · United States