Ship Island

Ship Island was the Union's unsinkable base in the Gulf — a barrier island twelve miles offshore with the only deep-water anchorage between Mobile and the Mississippi, seized by the Confederacy in January 1861 and abandoned back to the Union that September when the South realized it couldn't hold an island without a navy. From that anchorage Benjamin Butler staged the assault that took New Orleans; fifteen thousand men camped on the sand at the peak in April 1862.

After New Orleans fell, the island changed function — from staging ground to prison. Union soldiers convicted of crimes in the occupied city were sent out to the island; civilian detainees followed. Then, in 1865, came the Confederate prisoners — nearly five thousand of them, most captured at Mobile Bay, held in open-air compounds on the sand by the 2nd Louisiana Native Guard, Black soldiers guarding the men who'd fought to keep them enslaved. One hundred fifty-three Confederates and more than two hundred sixty Federals died on the island, mostly of disease — the heat, the water, and the yellow fever that had dogged the fort's construction from the start.

The fort that watched it all — Fort Massachusetts, the Third System masonry work begun in 1859 and not finished until 1866 — is the island's one surviving structure: the casemates, the terreplein, the sally port, the brick walls standing in the Gulf wind. Everything else the army built — the barracks, the hospital, the machine shops, the wharves, two lighthouses — is gone, taken by hurricanes and sand.

Camille cut the island in half in 1969; Katrina widened the gap in 2005. The fort survived both. The barrier island that staged the fall of New Orleans and held five thousand prisoners keeps its masonry — the sea is taking the rest back grain by grain.