Wampum Underground, Pennsylvania

This former underground limestone mine in western Pennsylvania, across from a large Cemex cement plant in Wampum, has been turned into a multi-tenant business park. For some years it was known as the Gateway Commerce Center, but is now called Wampum Underground. It was mined from the 1870s to 1946, leaving 2.5 million square feet of excavated space, with more than a million of that now redeveloped into offices, warehouses, and storage. Records storage started with the General Services Administration in 1963, and now Underground Archives manages records and media. An optical company started working on a lab inside in 1965, which is now L3 Brashear’s high-tech construction facility for sensitive optics used on observatories and satellites. There is also storage for RVs and self storage.