From 1880 to 1931, an extensive iron mine operated near the city of Florence in northeast Wisconsin. These 21 maps from its middle years of operation are the only surviving records of what exists below the surface. These maps are of historical interest for their record of surface features that are no longer in existence. They may also have potential practical value today as the site is being developed as residential and recreational property. Long after mining has ceased, improperly backfilled shafts and pits can pose subsidence hazards, and mine workings can result in expensive loss or damage to tools used to drill water wells. Includes a brief report that documents the history of the maps and how to read them.