The long history of Fort Moultrie on Sullivan's Island involves nearly every war this country has been involved since 1776 through WWII. The reason the State flag of SC has a palmetto tree on it is based upon a battle against the British Royal Navy in 1776. The fort, named Fort Sullivan at the time, was hastily constructed using the locally available palmetto trees cut to 10' and backfilled with sand to protect Charleston harbor. After a 10 hour naval bombardment from the British, the shells were absorbed by the soft palmetto wood, did not crack and some even bounced off. The 31 guns for the fort manned by over 400 patriots and lead by Col. William Moultrie inflicted heavy damage to the 9 British ships. It was a huge victory for the patriots, saving Charleston, for the time, from British capture and the fort was named after Moultrie after the battle. The palmetto tree became know for the bend not break strength of the 2nd SC Regiment and was later placed on the state flag in 1861.
https://en.wikipedia.org/wiki/Fort_Moultrie
