From Wikipedia

The Civil War
Episode Five

The Universe Of Battle

Winfield Scott, the commanding general of the U.S. Army, devised the Anaconda Plan to win the war with as little bloodshed as possible. His idea was that a Union blockade of the main ports would weaken the Confederate economy; then the capture of the Mississippi River would split the South. Lincoln adopted the plan, but overruled Scott's warnings against an immediate attack on Richmond.

In May 1861, Lincoln enacted the Union blockade of all Southern ports, ending regular international shipments to the Confederacy. When violators' ships and cargoes were seized, they were sold and the proceeds given to Union sailors, but the British crews were released. By late 1861, the blockade stopped most local port-to-port traffic. The blockade shut down King Cotton, ruining the Southern economy. British investors built small, fast "blockade runners" that traded arms and luxuries brought in from Bermuda, Cuba and the Bahamas in return for high-priced cotton and tobacco. Shortages of food and other goods triggered by the blockade, foraging by Northern armies, and the impressment of crops by Confederate armies combined to cause hyperinflation and bread riots in the South.

On March 8, 1862, the Confederate Navy waged a fight against the Union Navy when the ironclad CSS Virginia attacked the blockade; against wooden ships she seemed unstoppable but the next day she had to fight the new Union warship USS Monitor in the Battle of the Ironclads. The battle ended in a draw, which was a strategic victory for the Union in that the blockade was sustained. The Confederacy lost the Virginia when the ship was scuttled to prevent capture, and the Union built many copies of Monitor. Lacking the technology to build effective warships, the Confederacy attempted to obtain warships from Britain. The Union victory at the Second Battle of Fort Fisher in January 1865 closed the last useful Southern port and virtually ended blockade running.