To protect Texas against Federal invasion during the Civil War, Confederate General John B. Magruder ordered the construction of a fort at this site on September 4, 1863, four days before the famous Confederate victory won by Dick Dowling and his small company against Union ships and gunboats at Sabine Pass (7 mi. NE). After the Federal retreat, the Confederate Coastal Defense program continued, since Federal blockading vessels still patrolled Gulf waters and the threat of more invasions was feared. A storm on September 19 sent the Union patrol steamers out to sea, but drove ashore their coaling ship, the "Mannahassett". Confederate troops dismantled the ship and seized its cargo. Col. Valery Sulakowski, formerly of the Austrian Army, designed Fort Manhassett, whose name evidently was adapted from that of the captured ship. Major Getulius Kellersberger, a Swiss-born engineer who had settled in America some years earlier, oversaw the construction. By October 1863, five companies garrisoned the five redoubts of the new fort and manned its ten cannons. Fort Manhassett soldiers participated in the capture of two Union ironclad ships at Calcasieu Pass, Louisiana on May 6, 1864.