Hidden · Tower, Minnesota, United States
Soudan Underground Mine
Minnesota's oldest and deepest iron mine, where a 1924 electric hoist has carried visitors down toward level 27, and where physicists once hunted for neutrinos.
A rich iron mine that went from open pit to 2,341 feet down.
The Soudan Underground Mine is a Minnesota state park on the south shore of Lake Vermilion, in the Vermilion Range of the north. It is known as the state's oldest, deepest and richest iron mine, and it is a National Historic Landmark.
Prospectors looking for gold in the late 19th century found veins of hematite that often held more than 65 percent iron. An open pit started in 1882 and moved underground by 1900 for safety reasons. From 1901 until mining ended in 1962 the mine belonged to the Oliver Iron Mining division of United States Steel.
By 1912 the workings were 1,250 feet deep. When the mine closed, level 27 was being developed at 2,341 feet, and the tunnels, adits and raises together added up to more than fifty miles.
From ore to physics, and back to visitors.
Miners used a method called cut and fill: they took ore from the ceiling and raised the floor with waste rock, so floor and ceiling stayed 10 to 20 feet apart. It suited Soudan because the hematite was strong and the surrounding greenstone was weak. In 1965 U.S. Steel gave the mine to the State of Minnesota for educational use.
In the 1980s University of Minnesota scientists began using the mine for physics experiments, because the deep rock lets in very few cosmic rays. The laboratory hosted the Soudan 1 and Soudan 2 proton decay experiments, the MINOS neutrino detector and several dark matter searches. Public tours of the lab ended around 2016.
A fire in the main shaft on March 17, 2011, was smothered with 70,000 gallons of foam, and underground tours resumed in May 2012. Rain flooded the mine on June 18, 2024, damaging pumps, electrical systems and several trains. Underground tours have since resumed. In 2014 the mine park was combined with the neighboring Lake Vermilion State Park.
The mine above and below ground.
Practical notes.
Before you go.
Can you go underground at Soudan Mine?
Yes, guided underground tours have been offered, riding the 1924 electric hoist to level 27. Tours were interrupted by flooding in 2024 and have since resumed, so check the Minnesota DNR website for current details.
How deep is the mine?
Level 27, the deepest, is 2,341 feet below the surface. The workings include more than fifty miles of tunnels, adits and raises.
Why was there a physics laboratory in a mine?
The deep rock keeps cosmic rays to a very low level, which makes it a quiet place for sensitive experiments. The lab hosted proton decay, neutrino and dark matter research before it closed around 2016.
Who owns Soudan Mine now?
The State of Minnesota. U.S. Steel gave it to the state in 1965 for educational use, and it is managed as a state park by the Department of Natural Resources.
Around Minnesota
Walking tours, day trips and experiences around this area, on GetYourGuide.