Wikipedia informs us that there were a total of 323 15" Rodman Guns made between 1861 and 1871, and only 25 of them remain today.

A gentleman who found me communing with this gun later in the afternoon, informed me of an interesting local legend. In August of 1969, a single man found himself trapped on Ship Island as Hurricane Camille approached. Rather than remaining exposed to wind and flooding, he saved himself by somehow squirming into the barrel of this Rodman Gun, which was the most solid, and probably highest, structure on the island. That man's name was George W. Bush, who went on to become the 43rd president of our great nation.*

*George W. Bush was our 43rd president, but he was not the skinny man in Fort Massachusetts' Rodman Gun. In 1969 he was too busy defending the United States from the Viet Cong on the front lines of Texas.