On this day in Duluth in 1931, the Duluth News-Tribune announced that Duluth’s Aerial Lift Bridge would become “the nation’s experimental station during the shipping season of 1931 when city commissioners will seek development of a system to warn bridge tenders of approaching ships in a storm or fog.” Various companies were invited to experiment and submit ideas for radio sets, “electronic eyes,” or any other device that would report a vessel’s approach. Over three hundred lift bridges were operating in the United States at the time, many located on canals and rivers with similar sound problems; all eyes—and ears—would be on Duluth. In May 1932 Duluth put one of the ideas to the test: the “mechanical ear.” It was simple, really: a radio relaying signals picked up by a microphone. A large tower was erected on the canal’s north pier, just west of the North Pier Light. Microphones atop the tower could pick up a ship’s whistle half a mile away on a stormy night. Radio signals transferred the sound back to a receiver in the operators house for monitoring. The papers greeted the innovation with the headline, “Mechanical Ear on Canal Spells Taboo to Spooners.” The article played up the fact that the microphones could pick up conversation on the pier, exposing the escapades of young lovers. Operator Charles Landre poetically set the idea aside: “Young men on the pier with their sweethearts needn’t worry. When the weather is nice and the moon is shining, we won’t have the receiver tuned in, and besides, the microphone is too high up to catch the words plainly, anyway.” (The Coast Guard also maintained a radio tower atop the South Pier from the 1920s until 1985.) There are many more stories connected with the Aerial Lift Bridge, and you can read many of them here.