Louisiana in the American Civil War

Louisiana declared that it had seceded from the Union on January 26, 1861. Civil-War era New Orleans, the largest city in the South, was strategically important as a port city due to its southernmost location on the Mississippi River and its access to the Gulf of Mexico. The U.S. War Department early on planned for its capture. The city was taken by U.S. Army forces on April 25, 1862. Because a large part of the population had Union sympathies (or compatible commercial interests), the U.S. government took the unusual step of designating the areas of Louisiana then under U.S. control as a state within the Union, with its own elected representatives to the U.S. Congress. For the latter part of the war, both the U.S. and the Confederacy recognized their own distinct Louisiana governors. Similarly, New Orleans and 13 named parishes of the state were exempted from the Emancipation Proclamation, which applied exclusively to states in rebellion against the Union.

Politics and strategy in Louisiana

Secession

On January 8, 1861, Louisiana Governor Thomas Overton Moore ordered the Louisiana militia to occupy the U.S. arsenal at Baton Rouge and the U.S. forts guarding New Orleans, Fort Jackson and Fort St. Philip. A wealthy planter and slave holder, Moore acted aggressively to engineer the secession of Louisiana from the Union by a convention on January 23. Only five percent of the public were represented in the convention, and the state's military actions were ordered before secession had been established—in defiance of the state constitution, which called for a popular referendum to establish a convention. Moore attempted to justify these actions, saying: "I do not think it comports with the honor and self-respect of Louisiana as a slave-holding state to live under the government of a Black Republican president", using an epithet for Republicans used by many Democrats at the time.

The strategies advanced to defend Louisiana and the other Gulf states of the Confederacy were first, the idea of King Cotton; that an unofficial embargo of cotton to Europe would force Britain to use its navy to intervene in protecting the new Confederacy. The second was a privateer fleet established by the issue of letters of marque and reprisal by President Jefferson Davis, which would sweep the sea clear of U.S. naval and commercial ships, and at the same time sustain Louisiana's booming port economy. The third was a reliance on the ring of pre-war masonry forts of the Third System of American coastal defense, combined with a fleet of revolutionary new ironclads, to safeguard the mouth of the Mississippi from the U.S. Navy. All of these strategies were failures.

In March 1861, George Williamson, the Louisianan state commissioner, addressed the Texan secession convention, where he called upon the slave states of the U.S. to declare secession from the Union in order to continue practicing slavery:

With the social balance wheel of slavery to regulate its machinery, we may fondly indulge the hope that our Southern government will be perpetual ... Louisiana looks to the formation of a Southern confederacy to preserve the blessings of African slavery ...

— George Williamson, speech to the Texan secession convention (March 1861).

One Louisianan artillery soldier gave his reasons for fighting for the Confederacy, stating that "I never want to see the day when a negro is put on an equality with a white person. There is too many free niggers ... now to suit me, let alone having four millions."

Union plans

The Union's response to Moore's leveraged secession was embodied in U.S. President Abraham Lincoln's realization that the Mississippi River was the "backbone of the Rebellion." If control of the river were accomplished, the largest city in the Confederacy would be taken back for the Union, and the Confederacy would be split in half. Lincoln moved rapidly to back Admiral David Dixon Porter's idea of a naval advance up the river to both capture New Orleans and maintain Lincoln's political support; by supplying cotton to northern textile manufacturers and renewing trade and exports from the port of New Orleans. The U.S. Navy would become both a formidable invasion force and a means of transporting Union forces, along the Mississippi River and its tributaries. This strategic vision would prove victorious in Louisiana.