Iron Forge Discovery Map

The remains of an iron forge mill were uncovered in Anne Arundel County during installation of sewer line improvements for Baltimore/Washington International Thurgood Marshall Airport (BWI Marshall) within Patapsco Valley State Park. The purpose of this section of the MAA web site is to fulfill the regulatory requirement of the Maryland Historical Trust to compensate for unavoidable construction impacts to the iron forge site.

The iron forge mill was part of a complex of industrial buildings and features that may have been in operation as early as the mid- to late 1700’s. Identified features included:

  • The forge mill foundation and its associated wheel pit and headrace (conduit through which water flowed to the mill)
  • The foundation of Selby Mill, a grist mill, and its associated headrace
  • Road traces

Such discoveries help us better understand Maryland’s rich manufacturing heritage and help us learn more about the 18th and 19th centuries in Maryland’s Patapsco Valley.

This discovery was unexpected. A previous cultural survey had not identified significant archaeological sites in the vicinity of the proposed sewer route.

A portion of the sewer installation was constructed using jack and bore methods. The jack and bore drills a horizontal tunnel approximately 8 feet below the ground surface. Resources located closer to the ground surface are not generally affected. In this case, however, the drill bit became stuck in the stone foundation wall of the forge, which extended 11 feet below the surface. After consultation with the Maryland Historical Trust (MHT) and Department of Natural Resources (DNR), it was agreed that the jack and bore would be allowed to proceed along its current course following documentation of existing features.

This site provides a description of the findings of the archaeological field documentation process. It also explains how an iron forge operated, gives a glimpse of the iron industry in Maryland in the 18th and 19th centuries, and provides other resources you may wish to consult to learn more.


The forge site is located in Anne Arundel County, immediately east of Elkridge and south of Baltimore, within a portion of Patapsco Valley State Park. Stony Run runs along the east side of the site and drains in the Patapsco River to the north. Small streams and springs dot the surrounding landscape.

The vicinity has been known since historic times for its rich mineral resources, particularly iron. Iron occurs in the form of bog iron (iron ore) and hematite-rich clays. Archival records from the 18th and 19th centuries refer to the surrounding areas as “Mineral Ridge” and “Iron Hill.” Even during the initial boring for the sewer installation, boulders of bog iron were encountered and removed in order to allow the boring equipment to continue.