Historic Places. As of 2021, the surface buildings are open to the public, and during the summer months there are daily tours of the mine. Visitors are lowered in the antique 1924 electric mine hoist to level 27, the mine's lowest level at 2,341 feet (713.5 m) below ground. As of 2021, tours of the previously active underground physics laboratory were no longer offered. Lake Vermilion State Park, originally separate from Soudan Underground Mine State Park, began with the purchase of about 3,000 acres from U.S. Steel in 2010. The park includes the Stuntz Bay Boathouse Historic District. In 2014, the two adjacent parks were combined into one. Underground laboratory In the 1980s, scientists from the University of Minnesota began to develop the Soudan Mine as a site for sensitive physics experiments because of the very low rate of cosmic rays in the deep underground site, and also because they could inexpensively use the still-operating mine hoist. The mine laboratory was originally home to the Soudan 1 proton decay experiment and its successor, Soudan 2 which operated from 1989-2001. The University and the Minnesota Department of Natural Resources later expanded the laboratory to accommodate other physics projects, such as the MINOS neutrino detector, dark matter search experiments CDMS-II, SuperCDMS, and CoGeNT, and also a work on electroforming copper to create pure radiation free copper. Low-background materials screening facilities were in use and in continuing development. The mine was proposed as one possible site for a U.S. Deep Underground Science and Engineering Laboratory, but that project was instead awarded to the Homestake Mine (South Dakota). Parts of the laboratory had been open for daily tours, and there was an annual open house with more access to the facilities and representatives of the experiments to help with the tours and answer questions. The laboratory, along with public tours, were closed circa 2016. 2011 fire A fire broke out late on March 17, 2011, in the main shaft at the 25th level. The fire was smothered using 70,000 gallons of fire-fighting foam, filling the 27th and lowest level of the shaft (27th level) from floor to ceiling. The Underground Laboratory lost power but remained safe. The mine tours were closed for the summer of 2011, but the above ground tours and interpretive center reopened. After a major cleanup effort, underground tours resumed on May 26, 2012. See also List of National Historic Landmarks