On September 13, 1864, Major-General Samuel Jones sent, by way of his Assistant Adjutant-General, an order to Brigadier-General Beverly Robertson, commanding the Second and Sixth Military Districts of South Carolina:
General: The engineers are just about commencing the erection of a work on John’s Island opposite Battery Pringle. The force on James Island has been very much reduced, and if the enemy attempt to drive away the working parties, as they probably will, they may succeed, unless assistance is given by you.
The major-general commanding, therefore, directs you to send to this point as large a cavalry force as you can to protect the working parties and keep up a picket-line as near Legareville as practicable to guard against any sudden advance of the enemy, and prevent the escape of the negroes employed. If you can do so, send also a section of artillery with orders to retire into the new works; if forced back the cavalry to retire by the river road on John’s Island.
The fortification mentioned in this order would eventually receive the name “Fort Trenholm.” If you’ve been following my descriptions of the Charleston defenses, as they evolved 150 years ago, you are familiar maps such as this:
You see Fort Trenholm on the far left and on the west side of the Stono River. In the past, I’ve displayed these maps with the caveat that the maps depicted the final state of works around Charleston. Well, this was the last major fortification added to the Confederate lines defending Charleston. Now I can say, the map depicts what was there 150 years ago as we’ve caught up!
As described in the order, Fort Trenholm complemented Battery Pringle. During all the activity in July 1864, the Confederates realized just what Rear-Admiral Dahlgren observed – if the Federals had the forces to occupy John’s Island, they could make Battery Pringle untenable. So this addition to the far right of the Confederate line secured a vulnerable flank. When completed, any Federal warships attempting to move up the Stono River would have a crossfire to contend with. Not unlike that which caused the capture of the USS Isaac Smith in January 1863.
Robertson’s orders required him to secure John’s Island with a picket line down to Legareville during the construction of the works. In part, that was to keep the Federals from interfering, but also to prevent the escape of laborers employed in the work. But for the most part, the Federals, with limited resources, were not in a position to contest this addition to the line.
Being the last major fort built outside Charleston, Fort Trenholm never received a full complement of guns. But despite being built so late in the war, the works survived and is still there today, just north of the Charleston Airport:
While protected within the boundaries of the airport, unfortunately its location makes close inspection rather difficult. But it is there, as a mark of war.
(Citation from OR, Series I, Volume 35, Part II, Serial 66, pages 622-3.)