The Union blockade in the American Civil War was a naval strategy by the United States to prevent the Confederacy from trading.The blockade was proclaimed by President Abraham Lincoln in April 1861, and required the monitoring of 3,500 miles of Atlantic and Gulf coastline, including 12 major ports, notably New Orleans and Mobile. Many attempts to run the blockade were successful, but those ships fast enough to evade the Union Navy could only carry a small fraction of the supplies needed.