The Charleston County Sheriff's office was called to investigate, and brought in its bomb technicians along with specialists from the U.S. Air Force.
The technicians decided to transport some of the cannonballs to a nearby Navy base to be destroyed, but police had to shut down a section of the beach as some of the 150-year-old explosives were detonated in place where they were found, in the city of Folly Beach.
By evening, police gave the all clear and re-opened the beach.
The first shots of the Civil War were fired in nearby Fort Sumter on April 12, 1861.
Hurricane Matthew brought a nearly 6-foot storm surge and torrential rain that totaled 14 inches in spots to the Palmetto state, and is being blamed for two deaths there and at least 21 across four southeastern states.