On Minnesota’s Vermilion Range, this state park centers on the historic Soudan Underground Mine, famed as the state’s oldest, deepest, and richest iron mine. Exceptionally rich hematite discovered by prospectors led to open-pit mining in 1882 and underground mining by 1900. The mine later reached 2,341 feet deep, with more than fifty miles of underground workings, and became known for its cut-and-fill method suited to strong ore and weaker surrounding rock. After closing in 1962, the site was donated for educational use, later expanded and merged with nearby parkland, and also became an important underground laboratory for physics research.