During the American Civil War, the Union, also known as the North, referred to the United States led by President Abraham Lincoln. It was opposed by the secessionist Confederate States of America (CSA), informally called "the Confederacy" or "the South". The Union is named after its declared goal of preserving the United States as a constitutional union. "Union" is used in the U.S. Constitution to refer to the founding formation of the people, and to the states in union. In the context of the Civil War, it has also often been used as a synonym for "the northern states loyal to the United States government;" in this meaning, the Union consisted of 20 free states and five border states.

The Union Army was a new formation comprising mostly state units, together with units from the regular U.S. Army. The border states were essential as a supply base for the Union invasion of the Confederacy, and Lincoln realized he could not win the war without control of them, especially Maryland, which lay north of the national capital of Washington, D.C. The Northeast and upper Midwest provided the industrial resources for a mechanized war producing large quantities of munitions and supplies, as well as financing for the war. The Northeast and Midwest provided soldiers, food, horses, financial support, and training camps. Army hospitals were set up across the Union. Most Northern states had Republican governors who energetically supported the war effort and suppressed anti-war subversion, particularly that that arose in 186364. The Democratic Party strongly supported the war at the beginning in 1861, but by 1862, was split between the War Democrats and the anti-war element known as Peace Democrats, led by the extremist "Copperheads". The Democrats made major electoral gains in 1862 in state elections, most notably in New York. They lost ground in 1863, especially in Ohio. In 1864, the Republicans campaigned under the National Union Party banner, which attracted many War Democrats and soldiers and scored a landslide victory for Lincoln and his entire ticket against Democratic candidate George B. McClellan.

The war years were quite prosperous except where serious fighting and guerrilla warfare ravaged the countryside. Prosperity was stimulated by heavy government spending and the creation of an entirely new national banking system. The Union states invested a great deal of money and effort in organizing psychological and social support for soldiers' wives, widows, and orphans, and for the soldiers themselves. Most soldiers were volunteers, although after 1862 many volunteered in order to escape the draft and to take advantage of generous cash bounties on offer from states and localities. Draft resistance was notable in some larger cities, especially in parts of New York City, with its massive anti-draft riots of July 1863 and in some remote districts such as the coal mining areas of Pennsylvania.

Mobile ( moh-BEEL, French: [mɔbil] (listen)) is the county seat of Mobile County, Alabama, United States. The population within the city limits was 195,111 as of the 2010 United States Census, making it the third-most-populous city in Alabama, and the most populous in Mobile County.

Alabama's only saltwater port, Mobile is located on the Mobile River at the head of the Mobile Bay and the north-central Gulf Coast. The Port of Mobile has always played a key role in the economic health of the city, beginning with the settlement as an important trading center between the French colonists and Native Americans, down to its current role as the 12th-largest port in the United States.Mobile is the principal municipality of the Mobile metropolitan area. This region of 412,992 residents is composed solely of Mobile County; it is the third-largest metropolitan statistical area in the state. Mobile is the largest city in the Mobile–Daphne−Fairhope CSA, with a total population of 604,726, the second largest in the state. As of 2011, the population within a 60-mile (100 km) radius of Mobile is 1,262,907.Mobile was founded in 1702 by the French as the first capital of Louisiana. During its first 100 years, Mobile was a colony of France, then Britain, and lastly Spain. Mobile became a part of the United States in 1813, with the annexation by President James Madison of West Florida from Spain. The city surrendered to Federal forces on April 12, 1865, after Union victories at two forts protecting the city. This, along with the news of Johnston's surrender negotiations with Sherman, led Taylor to seek a meeting with his Union counterpart, Maj. Gen. Edward R. S. Canby. The two generals met several miles north of Mobile on May 2. After agreeing to a 48-hour truce, the generals enjoyed an al fresco luncheon of food, drink, and lively music. Canby offered Taylor the same terms agreed upon between Lee and Grant. Taylor accepted the terms and surrendered his command on May 4 at Citronelle, Alabama.Considered one of the Gulf Coast's cultural centers, Mobile has several art museums, a symphony orchestra, professional opera, professional ballet company, and a large concentration of historic architecture. Mobile is known for having the oldest organized Carnival or Mardi Gras celebrations in the United States. Its French Catholic colonial settlers celebrated this festival from the first decade of the 18th century. Beginning in 1830, Mobile was host to the first formally organized Carnival mystic society to celebrate with a parade in the United States. (In New Orleans, such a group is called a krewe.)