Between the years of 1861 and 1865 the United States was divided as a nation, into the confederate forces of the United States, and the Union of the United States. The Union Navy worked to blockade the Atlantic Coast of the United States around the Confederated States, (the Southern United States). The Union Blockade also extended around the Gulf Coast. Ships from the Union Navy blocked these vital ports. The Union wanted to prevent the Confederate States of America from receiving supplies, men and food. The Union wanted to try and choke off resupply to the South, and to prevent the shipment of arms, ammunition and material to the Southern States.
The ships that the Confederacy tried to use to evade the Union ships were mostly small, fast high-speed ships that had small cargo or carrying capacity. These ships were called blockade-runners, and they were supported and operated by sympathetic forces from Britain. They allowed volunteer Royal Navy officers to take a leave of absence, and many of these British Officers manned these ships and assisted the Confederacy. They ran illicit cargo runs in violation of the Union blockade from Nassau, The Bahamas, and Bermuda, where the British has obligingly set up Confederate resupply bases.
Acting in defense of the Nation and in the best interests of the Union, President Abraham Lincoln set up the massive blockade effort on April 19th, 1861. The United States Navy operating under the President and Union command commissioned over 500 ships, and while often rag tag in appearance, they were greatly successful, leading to the capture or destruction of nearly 1,500 smaller, Confederate Blockade runner ships.
Even with the valiant effort of the Union Navy, generally the blockade was a mixed bag, with nearly 80 percent of the attempts to run the blockade successful. But because it was forced to have small ships carrying small amounts of goods, the Confederacy slowly ground to a halt, cotton exports were reduced over 95 percent. No nation can stand against itself, and eventually the Civil War, in all of its bloody battle action drew to a close. While successful in scope, the actions of the U.S. Navy and Union Naval forces during the Civil War were very rough on the nation as a whole, and it was several decades until the U.S. Navy successfully healed from having its forces divided in such a manner.