The blockade runners of the American Civil War were specially outfitted Confederate ships designed to slip through the blockade of Southern by the Union Navy during the American Civil War. On April 19, 1861, one week after Confederate forces attacked Fort Sumter, President Abraham Lincoln ordered the blockade. In response, the Confederacy used small fast ships known as blockade runners. During the first two years of the Civil War, the blockade had very limited success. As many as two out of every three ships entering or leaving Southern ports were successful. The Union Navy had to patrol nearly 3,500 miles of seashore along the Atlantic and Gulf coastlines. But as the Union built more ships, the blockade became more effective. As few as 25% of blockade runners were successful later in the war. 