Charleston was an incredibly important city in the South because of its location--it was located on a prime piece of coast line that made importing and exporting goods relatively fast and easy.
It depends on which war you're referring to. I feel that the answer you're looking for is the radio, though.
Answer: In the West, Americans found a lot of land to expand, new species of plants and animals, and access to the Pacific Ocean. Because of their access to the largest body of water on the planet, international trade was possible (but wouldn't begin for another 75 or so years, assuming that this is in the mid-1800s).
