Duluth’s unique Aerial Lift Bridge, the only one on the planet with a top span, was converted form a transfer bridge that was also unique: the only stiff-girded transfer bridge and the only ever built in North America. And just like the lift bridge, many people mistakenly believe Duluth’s transfer bridge was the first one ever built. In fact, it was the world’s third transfer bridge, modeled on the work of French bridge engineer Ferdinand Arnodin. Arnodin’s design had to be altered to work in Duluth’s cold climate and narrow canal, which made the DUluth bridge unique. Read the full story of Arnodin’s revolutionary bridge and how Duluth’s city engineer Thomas McGilvray and bridge engineer C. A. P. Turner altered it to work in Duluth here.