THE SEARCH FOR A REVOLUTIONARY WAR-ERA PRIVATEER, THE BRIGANTINE FREEMASON, MARBLEHEAD HARBOR, MASSACHUSETTS

The privateer Freemason was a 16-gun, American brigantine vessel used to raid British supply ships during the American Revolution. On September 30th, 1779 while in Marblehead Harbor and a year after it was recaptured from the British frigate Savage by the privateer Speedwell, it caught fire and blew up at anchor. According to records, the chief gunner accidentally dropped a piece of slow-match into netting that ran alongside the vessel after sounding the evening gun. The gunner, along with the few sailors aboard, escaped the burning ship and reached shore before the Freemason exploded; sending its ordnance and debris smashing into the houses along the waterfront. Parts of the ship were salvaged three days after the explosion.

During May of 2008, a research team from UMass-Boston and the Massachusetts Board of Underwater Archaeological Resources set out to locate where the Freemason may have came to rest. Historical accounts of the event coupled with knowledge that she blew up while at anchor aided in our search. We planned to look for possible ballast piles, cannons, and other iron fittings or cannonballs that would have settled after the event. Due to the age of the wreck and fact that she caught fire and exploded, her masts or timbers were not expected to be found.

During our search, we collected sidescan sonar imagery, subsurface profiles, and magnetometer readings throughout Marblehead Harbor, totaling approximately 9 line kilometers. The results of the magnetometer survey showed significant concentrations of ferrous material throughout the Harbor. This was expected since the Harbor was already populated with moored vessels and the town uses steel barges for the town dock. All of these were in close proximity to the survey lines. Unfortunately, the sidescan imagery yielded no surficial expression of a shipwreck and the subbottom data showed several anomalous features that will require additional investigation.

During the survey, the team also investigated the location of a “mystery shipwreck” located just outside the Harbor. Analysis of the data from this site is ongoing and initial interpretations suggest a ballast pile with large concentrations of ferrous material partially buried in the sediment.