The Union blockade failed to stop the majority of ships that tested it, but successfully prevented much of the Confederacy's pre-war international trade.

Much of the postwar debate has focused on the effectiveness of the Anaconda Plan and the Confederate blockade. One Southern account considered it a "fact joke" while another claimed it was strangulation. In terms of foreign trade, it is true that most ships trying to get through the Union blockade succeed - about 1,000 of the 1,300 foreign ships pass through unharmed - but this fact is only part of the large impact of the blockade. Although a total of 8,500 commercial ships, including domestic Confederate ships, had docked in the South during the war, the volume of trade was a far cry from the 20,000 ships that docked in the years 1856 - 1860. The trade-in cotton, the most profitable crop in the South, plummeted 95 percent during the war. Although the bravery of the blockaders provided the Confederacy with much-needed war materials and made European merchants rich, the blockade successfully suppressed a large portion of the Southern economy.

The Union blockade in the American Civil War was a naval strategy by the United States to prevent the Confederacy from trading. Those blockade runners fast enough to evade the Union Navy could carry only a small fraction of the supplies needed. They were significantly operated by foreign citizens, making use of neutral ports such as Havana, Nassau, and Bermuda. During the Civil War, Union forces established a blockade of Confederate ports designed to prevent the export of cotton and the smuggling of war materiel into the Confederacy. The exports of cotton from the South fell by nearly 95 percent by the end of the war due to the Union Blockade. Blockade runners could make a lot of money if their ships and cargo successfully passed the blockade. The Union Navy captured or destroyed around 1,500 blockade runner ships during the course of the Civil War. The Union blockade became one of the facts about Civil War Navies.