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GPR Anomaly Ground-Truthing Reveals New Findings at the Fort Fisher State Historic Site

By Cyndi Goode, Ph.D., RPA, Principal Investigator/Laboratory Director and Alison Haller, M.S., Director of Marketing and Communications at Commonwealth Heritage Group, Inc.

Known as the “Gibraltar of the South”, Fort Fisher, was constructed to protect Wilmington, which was a vital seaport for Confederate blockade runners during the Civil War. Once through the Federal blockade, goods could be unloaded and shipped north to Petersburg, Virginia by way of the Wilmington and Weldon Railroad. The fort consisted of a land face battery on the north side that extended one-half mile across the peninsula, and a sea face battery on the east side that extended for a mile along the beach. On January 15, 1865 the Federal infantry assaulted the fort’s land face while sailors and marines attacked the sea face. The infantry attackers succeeded in scaling the earthen parapets on the north land face and fought hand-to-hand with the outnumbered Confederates between the batteries for five hours.

Portions of the parapet, gun emplacements, and traverse mounds on the north land face are still standing. However, until recently, many were unaware of the hidden infrastructure that lay below the fort. The North Carolina Department of Natural and Cultural Resources (NCDCR) contacted Commonwealth Heritage Group, Inc. (Commonwealth) to investigate ground-penetrating radar (GPR) anomalies that were identified during a recent survey, helping to uncover and identify subsurface structures under the parapet and traverse mounds.

Figure 1: Anomaly 1, collapsed passageway located under the parapet.

These investigations provided archaeological services for the characterization and preliminary evaluation of three GPR anomalies and were conducted in support of master planning for Fort Fisher’s site development. Working in consultation with the North Carolina State Historic Preservation Office (HPO) and the North Carolina Office of State Archaeology (OSA), Commonwealth’s archaeologist excavated seven test units, further investigating three GPR anomalies that provide insight on the hidden infrastructure.

Commonwealth provided the data for OSA to create a 3D photogrammetry model of the anomalies and conducted test excavations to identify their dimensions and structural characteristics. Two of the anomalies were collapsed, subsurface, wood-framed structures that contained burnt wood beams and planks. Anomaly 1 was a collapsed subterranean passageway that ran beneath the parapet and traverse mounds that made up the north land face of Fort Fisher.

Figure 2: Anomaly 4, collapsed, subsurface bombproof room or magazine under the traverse mound

Anomaly 4 was a collapsed bombproof room or magazine that extended north inside one of the traverse mounds. These wood-framed structures were built into the earthworks for use as cover during bombardments and would have been occupied by Confederate soldiers prior to the battle on January 15th, and by Union soldiers immediately afterward.

Figure 3: Drawing of bombproof room (Watts et al. 1981:Figure 26)

Other findings included one 0.58-caliber unfired Minié ball, one 0.57-caliber fired Enfield bullet, two unfired brass percussion caps, and several iron fasteners from the passageway and bombproof room wall.

Want to view the 3D photogrammetry model of the anomalies and conducted test excavations? Click here to view the tunnel unit (Anomaly 1), the Trench Unit (Anomaly 2), and the Magazine Unit (Anomaly 4).

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