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 of Atlantic and Gulf coastline, including 12 major ports, notably New Orleans and Mobile. Those blockade runners fast enough to evade the Union Navy could carry only a small fraction of the supplies needed. They were operated largely by British and French citizens, making use of neutral ports such as Havana, Nassau and Bermuda. The Union commissioned around 500 ships, which destroyed or captured about 1,500 blockade runners over the course of the war.
The blockade was successful in blocking 95% of cotton exports from the South compared to pre-war levels, devaluing its currency and severely damaging its economy. However, it was less successful in preventing war material from being smuggled into the South. Throughout the conflict, at least 600,000 arms (mostly British Pattern 1853 Enfield rifles) were smuggled by blockade runners to the Confederacy, 330,000 of them into the Gulf ports. Historians have estimated that supplies brought to the Confederacy via blockade runners that made it past the Union blockade lengthened the duration of the conflict by up to two years.
Proclamation of blockade On April 19, 1861, President Lincoln issued a Proclamation of Blockade Against Southern Ports: Whereas an insurrection against the Government of the United States has broken out in the States of South Carolina, Georgia, Alabama, Florida, Mississippi, Louisiana, and Texas, and the laws of the United States for the collection of the revenue cannot be effectually executed therein comformably to that provision of the Constitution which requires duties to be uniform throughout the United States:
And whereas a combination of persons engaged in such insurrection, have threatened to grant pretended letters of marque to authorize the bearers thereof to commit assaults on the lives, vessels, and property of good citizens of the country lawfully engaged in commerce on the high seas, and in waters of the United States: And whereas an Executive Proclamation has been already issued, requiring the persons engaged in these disorderly proceedings to desist therefrom, calling out a militia force for the purpose of repressing the same, and convening Congress in extraordinary session, to deliberate and determine thereon:
Now, therefore, I, Abraham Lincoln, President of the United States, with a view to the same purposes before mentioned, and to the protection of the public peace, and the lives and property of quiet and orderly citizens pursuing their lawful occupations, until Congress shall have assembled and deliberated on the said unlawful proceedings, or until the same shall ceased, have further deemed it advisable to set on foot a blockade of the ports within the States aforesaid, in pursuance of the laws of the United States, and of the law of Nations, in such case provided. For this purpose a competent force will be posted so as to prevent entrance and exit of vessels from the ports aforesaid. If, therefore, with a view to violate such blockade, a vessel shall approach, or shall attempt to leave either of the said ports, she will be duly warned by the Commander of one of the blockading vessels, who will endorse on her register the fact and date of such warning, and if the same vessel shall again attempt to enter or leave the blockaded port, she will be captured and sent to the nearest convenient port, for such proceedings against her and her cargo as prize, as may be deemed advisable.
And I hereby proclaim and declare that if any person, under the pretended authority of the said States, or under any other pretense, shall molest a vessel of the United States, or the persons or cargo on board of her, such person will be held amenable to the laws of the United States for the prevention and punishment of piracy.
In witness whereof, I have hereunto set my hand, and caused the seal of the United States to be affixed.
Done at the City of Washington, this nineteenth day of April, in the year of our Lord one thousand eight hundred and sixty-one, and of the Independence of the United States the eighty-fifth.
Constitutionality of the blockade In 1863, in the Prize Cases, the U.S. Supreme Court found that the blockade was constitutional.. The government's case was argued by U.S. Attorney Richard Henry Dana Jr., the author of Two Years Before the Mast.Jeffrey L. Amestoy, "The Supreme Court Argument that Saved the Union: Richard Henry Dana, Jr., and the Prize Cases", Journal of Supreme Court History, vol. 30, no. 1 (March 2010), pp. 10–24.
Operations Scope A joint Union military-navy commission, known as the Blockade Strategy Board, was formed to make plans for seizing major Southern ports on the Atlantic Coast. The November 1861 capture of Port Royal in South Carolina provided the Union with an open ocean port and repair and maintenance facilities in good operating condition. It became an early base of operations for further expansion of the blockade along the Atlantic coastline,Time-Life, p. 31. including the Stone Fleet of old ships deliberately sunk to block approaches to Charleston, South Carolina. Apalachicola, Florida, received Confederate goods traveling down the Chattahoochee River from Columbus, Georgia, and was an early target of Union blockade efforts on Florida's Gulf Coast. Another early prize was Ship Island, which gave the Navy a base from which to patrol the entrances to both the Mississippi River and Mobile Bay. The Navy gradually extended its reach throughout the Gulf of Mexico to the Texas coastline, including Galveston and Sabine Pass.U.S Naval Blockade
With 3,500 miles (5,600 km) of Confederate coastline and 180 possible ports of entry to patrol, the blockade would be the largest such effort ever attempted. The United States Navy had 42 ships in active service, and another 48 laid up and listed as available as soon as crews could be assembled and trained. Half were sailing ships, some were technologically outdated, most were at the time patrolling distant oceans, one served on Lake Erie and could not be moved into the ocean, and another had gone missing off Hawaii.Soley, James Russel, The Blockade and the Cruisers At the time of the declaration of the blockade, the Union only had three ships suitable for blockade duty. The Navy Department, under the leadership of Navy Secretary Gideon Welles, quickly moved to expand the fleet. U.S. warships patrolling abroad were recalled, a massive shipbuilding program was launched, civilian merchant and passenger ships were purchased for naval service, and captured blockade runners were commissioned into the navy. In 1861, nearly 80 steamers and 60 sailing ships were added to the fleet, and the number of blockading vessels rose to 160. Some 52 more warships were under construction by the end of the year.Davis, Kenneth C. Don't Know Much About The Civil War. By November 1862, there were 282 steamers and 102 sailing ships. By the end of the war, the Union Navy had grown to a size of 671 ships, making it the largest navy in the world.
By the end of 1861, the Navy had grown to 24,000 officers and enlisted men, over 15,000 more than in antebellum service. Four squadrons of ships were deployed, two in the Atlantic and two in the Gulf of Mexico.Time-Life, p. 33.
Blockade service Blockade service was attractive to Union seamen and landsmen alike. Blockade station service was considered the most boring job in the war but also the most attractive in terms of potential financial gain. The task was for the fleet to sail back and forth to intercept any blockade runners. More than 50,000 men volunteered for the boring duty, because food and living conditions on ship were much better than the infantry offered, the work was safer, and especially because of the real (albeit small) chance for big money. Captured ships and their cargoes were sold at auction and the proceeds split among the sailors. When Eolus seized the hapless blockade runner Hope off Wilmington, North Carolina, in late 1864, the captain won $13,000 ($ today), the chief engineer $6,700, the seamen more than $1,000 each, and the cabin boy $533, compared to infantry pay of $13 ($ today) per month. The amount garnered for a prize of war widely varied. While the little Alligator sold for only $50, bagging the Memphis brought in $510,000 ($ today) (about what 40 civilian workers could earn in a lifetime of work). In four years, $25 million in prize money ($ today) was awarded. One sailor, Benjamin Jackson, earned $900 ($ today) after one year with the West Gulf Blockading Squadron.
Blockade runners
While a large proportion of blockade runners did manage to evade the Union ships, as the blockade matured, the type of ship most likely to find success in evading the naval cordon was a small, light ship with a short draft—qualities that facilitated blockade running but were poorly suited to carrying large amounts of heavy weaponry, metals, and other supplies badly needed by the South. They were also useless for exporting the large quantities of cotton that the South needed to sustain its economy.Wyllie, 2007 p. 184 To be successful in helping the Confederacy, a blockade runner had to make many trips; eventually, most were captured or sunk. Nonetheless, five out of six attempts to evade the Union blockade were successful. During the war, some 1,500 blockade runners were captured or destroyed.
Ordinary freighters were too slow and visible to escape the Navy. The blockade runners therefore relied mainly on new steamships built in Britain with low profiles, shallow draft, and high speed. Their paddle-wheels, driven by steam engines that burned smokeless anthracite coal, could make . Because the South lacked sufficient sailors, skippers and shipbuilding capability, the runners were mostly built, commanded and manned of officers and sailors of the British Merchant Marine. The profits from blockade running were high as a typical blockade runner could make a profit equal to about $1 million U.S. dollars in 1981 values from a single voyage. Private British investors spent perhaps £50 million on the runners ($250 million in U.S. dollars, equivalent to about $4.01 billion in 2026 dollars). The pay was high: a Royal Navy officer on leave might earn several thousand dollars (in gold) in salary and bonus per round trip, with ordinary seamen earning several hundred dollars.
The blockade runners were based in the British islands of Bermuda and the Bahamas, or Havana, in Spanish Cuba. The goods they carried were brought to these places by ordinary cargo ships, and loaded onto the runners. The runners then ran the gauntlet between their bases and Confederate ports, some apart. On each trip, a runner carried several hundred tons of compact, high-value cargo such as cotton, turpentine or tobacco outbound, and rifles, medicine, brandy, lingerie and coffee inbound. Often they also carried mail. They charged from $300 to $1,000 per ton of cargo brought in; two round trips a month would generate perhaps $250,000 in revenue (and $80,000 in wages and expenses).
Blockade runners preferred to run past the Union Navy at night, either on moonless nights, before the moon rose, or after it set. As they approached the coastline, the ships showed no lights, and sailors were prohibited from smoking. Likewise, Union warships covered all their lights, except perhaps a faint light on the commander's ship. If a Union warship discovered a blockade runner, it fired signal rockets in the direction of its course to alert other ships. The runners adapted to such tactics by firing their own rockets in different directions to confuse Union warships.