(WHTM) A week to the day after the bombardment of Fort Sumter, Abraham Lincoln declared the U.S. Navy would blockade the ports of the Confederate states. It would be a major undertaking-guarding 3,500 miles of coastline, 12 major ports, and over 170 smaller ports. It would be the largest blockade ever attempted.

And the Union didn’t have the navy to do it. When the war broke out the fleet had 90 ships, of which 48 sat at docks without crews. Many were obsolete, some being sail-only.

Navy Secretary Gideon Welles had the task of creating the blockade fleet, pretty much from scratch. He recalled navy ships sailing abroad, instituted a major shipbuilding effort, and purchased civilian ships to convert to military use. By the end of the war the Union navy was the biggest in the world, with 670 ships, and 24,000 officers and enlisted men.

As the blockade force got bigger and more effective, Confederate forces looked for ways to break the blockade. The best known were two innovative vessels-the ironclad C.S.S. Virginia and submarine Hunley. Both managed to sink Union ships, but the South lacked the resources and skills to turn out similar ships in enough quantity to put even a small dent in the blockade.

Far more effective were blockade runners, small ships which would attempt to slip in and out of ports without attracting the attention of blockaders. If spotted they relied on speed (and their shallow drafts) to escape. Most blockade runners were privately owned. A successful voyage could reap huge profits. But the things that made them successful (small size, shallow draft) also meant they couldn’t carry much cargo. And as the blockade grew, running the blockade became more risky.

There was profit in being a blockader as well. A captured vessel would be sold off, and prize money distributed to the crew of the ship that made the capture. Blockade duty was boring (most of the time), but it could be lucrative-and was certainly safer than being a soldier.

In all, the navy destroyed or captured somewhere around 1,500 blockade runners. (Many of the captured blockade runners were sold off to the navy.) By war’s end the blockade had done what it was supposed to do; it choked off Confederate access to foreign markets. They couldn’t export products (mostly cotton), or import food and weapons the Southern armies needed. Ultimately, this sped up the collapse of the Confederate war effort.