This marker at Fort Sumter explains the relationship between Morris Island and Fort Sumter. It reads:
1863-64 Map of the Defences of Charleston and the works erected by U.S. forces
Confederate batteries hidden in the dunes of Morris Island, directly in front of you, commanded the approach to Charleston Harbor. Union forces needed Morris Island, a key location from which to attack Fort Sumter, less than one mile away.
On July 18, 1863, a direct assault failed against Fort Wagner, a Confederate stronghold near Morris Island's north end. The Union then changed tactics, subjecting Fort Wagner to a two-month siege. The confederates finally evacuated, abandoning Morris Island on September 6, 1863. Union gunners then aimed powerful rifled cannon at Fort Sumter. In the next two years, massive bombardments reduced most of Fort Sumter to rubble.
Assault on Fort Wagner, July 18, 1863. The 54th Massachusetts Infantry, a black regiment, led the direct assault. Under intense fire, the 54th briefly gained Wagner's parapet, but fell back with heavy loss. Though the assault failed, it proved the courage of black troops and confirmed their military value for the Union.
In 1863-64 Confederates still held most of the strategic positions around Charleston Harbor. The Union Navy failed to take Fort Sumter by sea, and in June 1862 the Army failed against Secessionville, south of Charleston. Controlling Morris Island in 1863 enabled the Union to bombard Fort Sumter and Charleston.
Union soldiers at Battery Rosecrans, Morris Island, fire 100-pounder Parrott rifles at Fort Sumter, about two miles away. The Union bombardment continued for 22 months, one of the longest sieges in U.S. military history. Fort Sumter was decimated, but its Confederate garrison refused to surrender.