What would that cargo have been? Railroad iron? Not worth it because of the tariffs. Cost more to ship it from Europe than it was to buy it from Pennsylvania.
Oh wait! I think I see what's going on here!
It could have been any cargo a that a Charleston merchant wanted. What ever he was willing to pay for.
Your graphic of 1858 tariffs indicated that the Government collected about $47,800,000 in tariffs. Tariffs varied widely depending on what the imported item is. Just for argument sake, lets say that that dollar figure represents an average of 15% tariff on imported goods. That means that the total value of imports is somewhere around $318,000,000.
Who was buying those imports? Where were those goods going?