At least one 15” shell from the Federal Monitors Nahant, Patapsco and Passaic penetrated the sand and marsh-sod curtain wall of Confederate Fort McAlister, about 20 miles south of Savannah, Georgia, on March 3, 1863 during an intensive, 8 hour naval bombardment, before blowing up. The thickness of this stoutly built earthwork fort, where the penetration occurred, was measured by a CSA Artillery officer after the bombardment and he found it to be an astounding, 18 feet! Not one round penetrated the fort’s large bomb-proof or magazines.
Tracy and Mike
Dahlgren shells, like this one found at Fort McAlister, Georgia, were used for the very first time against CSA land fortifications on March 3, 1863.
I am standing on the river face of Fort McAlister about half way up. I’m 5’ 10” tall so the fort was 20 to 24 feet above the natural ground in 2006. Allowing for some settling and erosion, maybe it was 30 feet high in 1863. 10 feet thick at the top of the parapet and 30 to 40 feet thick at the bottom, we estimate that the Monitor’s shell penetrated a few feet higher than midway up the slope.