Fort Sumter is one of the most important sites in American History, and the National Park Service has treated it as such. In 1861, after the secession of South Carolina, Union forces evacuated the surrounding forts and batteries and braced themselves inside Fort Sumter, waiting for the day to come when the increasingly hostile Confederate states would cause a problem. The were right to worry.
In April 1861, President Lincoln sent a letter to the military commander in Charleston telling them that he was sending a ship to resupply his troops, who were down to their last rations. The day before the ship was scheduled to arrive, Confederate troops opened fire on the fort from all surrounding points. After a day and a half of merciless pounding from the Confederates, the battered, ill-supplied Union troops surrendered. The Confederate army managed to hold onto the Fort until 1865, when the city finally had to be evacuated. When the Union army took Ft. Sumter back, they found that it was little more than a pile of rubble.
Today, you can visit Ft. Sumter and see this important and endlessly fascinating site. Boats depart on multiple trips from both sides of the Cooper River. After taking an informative and pleasant boat trip, on which a recording tells you a little about the history of the important Charleston harbor and points out some of the other sites you pass on the way to the fort, you are given about an hour and a half at the fort.
The fort itself is in various states of disrepair. You can really see the pounding it took from the Union gunboats. There are many different cannons still at the site, so you get a good sense of the weaponry the soldiers were fighting with. There is also an excellent museum at the site that contains, among other things, the original flag that flew over the fort.
If you decide to take the boat from the Aquarium Wharf, there is a parking garage very close where I recommend parking. That departure point has a small museum about Charleston on the eve of the war and also has a neat little gift shop where you can stock up on unusual Civil War-related trinkets and books. Make sure to strike up a conversation with the volunteers who are working--they always have something interesting to say!
If you decided to leave from the Patriot's Point docks, you won't get to see the museum, but you will get free parking! That should certainly save you a few bucks.
Tickets are $12 for adults, $11 for seniors, and $6 for children 6-11. Kids under 6 are free. For more info, visit the Ft. Sumter website.
"Charleston: Where the Civil War Began and Someday it Will End!"