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March 20, 1902: Engineering News publishes drawings for Aerial Bridge

On this day in 1902, the Engineering News published drawings of the yet-to-be-built aerial transfer bridge that would span the Duluth Ship Canal. The drawings were by structural engineer C. A. P. Turner of the American Bridge Company, working off notes by Duluth City Engineer Thomas McGilvray that adapted Ferdinand Arnodin’s plans for the aerial transfer bridge he built over the River Seine at Rouen, France. But the story that accompanied the drawings was credited to William Patton, who had replaced McGilvray as city engineer. The bridge would be the first of its kind in the hemisphere and the only stiff-trussed transporter bridge in the world. The bridge’s plans were outlined in the City Engineer’s annual report of 1901: “The plans, as approved, are for a stiff riveted girder of 393 ft. 9 in. span, supported on steel towers resting on pile and concrete foundations, with the bottom chord of the bridge 135 ft. above high water. The ferry car is suspended by stiff, riveted hangers from trucks running on tracks placed within the bottom chords of the trusses. The car is proportioned to carry a loaded streetcar of 21 tons, and the remainder of the floor loaded with 110 pounds per square foot.” Read more about the aerial transfer bridge and aerial lift bridge here.

Plans for Duluth’s Aerial Transfer Bridge published in Engineering News March 20, 1902. (Image: Zenith City Press)