Total maritime tonnage at the Port of Duluth-Superior in 2023 increased 4.5% over the previous year, helped along by more than 21.5 million tons of iron ore — the most shipped in a single season since 1995, according to the port authority. Iron ore was up 12.6% from 2022, with increases in both domestic shipping and exports. Last month, the season closed with more than a million tons of iron ...