"The fort on the first hill in Dorchester:" Archeological investigations of Colonel Gridley's Revolutionary War star fort at Dorchester Heights, Boston National Historic Park, South Boston, Massachusetts

Mueller, James; Pendery, Steven; Griswold, William

Background studies and field testing resulted in the discovery of parts of a star fort that was built on Dorchester Heights in May 1776. The work was done as part of the Section 106 compliance for improvements to the grounds and monument of Dorchester Heights, a unit of Boston National Historic Park, in South Boston, Massachusetts. The archeology was primarily done by the National Park Service authors on National Park Service property. Background studies were done intermittently beginning in 1990, while one season of fieldwork was done each year between 1994 and 1996. This fort is unique in the region and rare in the United States because it is a Revolutionary War, earthen fort with masonry bridge abutments and powder house. The excavations were conducted in the undisturbed portions of the ditch, the entranceway, and the powder magazine. The lower half of the ditch as it had been dug into the native glacial drumlin was still intact with portions of a drainage cunette and a banquette-like step preserved at the base of the ditch. The ditch was filed, probably in 1852, when the first grading for Thomas Park was done, with imported loam, rather than with the hypothesized drumlin matrix from the parapets. Except for the gate area, the ditch fill contained no military artifacts and contained very few artifacts of any kind. The ditch floor was found very close to the elevation predicted from a study of 200 years of historic drawings and maps. The shape of the ditch floor and floor features are presumed to date to 1776 in the absence of contradictory evidence for 1812 modifications. Original, 1776 parts, as well as modifications fort the War of 1812, of the entranceway and powder magazine were uncovered. The entranceway consisted of the original, 1776 masonry bridge abutments for crossing the ditch at the south-facing arm of the western salient. Possibly, a horizontal retractable bridge may have been used by soldiers to cross the ditch with their cannons and equipment. The abutment included part of the original, 1776 drain that is thought to have carried surface water from the parade ground into the ditch. This drainage was disturbed several times to repair the underground bracing system for the gate that was probably located along the centerline of the parapets and in line with bridge crossing. The gate probably consisted of a double-door hung from vertical jambs that were supported by and underground sill threshold. The entranceway is located close to where it was shown on a 1776 drawing of the fort- on the somewhat protected south side of the fort, away from Boston and its harbor. The mortared, fieldstone foundation with supporting floor partitions and drains of the 1776 powder magazine were encountered. The magazine was small, but proportional to the size of the fort, and located underground, perhaps seven feet beneath the parade level of the north salient. Brick rubble suggesting a brick superstructure was found intramurally in the foundation. The magazine had been repaired or re-built in 1814 when the British threat during the War of 1812 increased; other repairs between 1776 and 1814 are possible. The location of the magazine under the exposed north salient on the Boston, harbor-side of the fort is surprising. Fragments of an officer’s epaulet were found in the rubble between the foundation walls and, except for musket balls from the ditch at the gate, comprise the only military artifact found during three field seasons.