Contraband was a term commonly used in the US military during the American Civil War to describe a new status for certain people who escaped slavery or those who affiliated with Union forces. In August 1861, the Union Army and the US Congress determined that the US would no longer return people who escaped slavery who went to Union lines, but they would be classified as "contraband of war," or captured enemy property. They used many as laborers to support Union efforts and soon began to pay wages.

United States Colored Troops (USCT) were Union Army regiments during the American Civil War that primarily comprised African Americans, with soldiers from other ethnic groups also serving in USCT units. Established in response to a demand for more units from Union Army commanders, by the end of the war in 1865 USCT regiments, which numbered 175 in total, constituted about one-tenth of the manpower of the army. Approximately 20 percent of USCT soldiers were killed in action or died of disease and other causes, a rate about 35 percent higher than that of white Union troops. Numerous USCT soldiers fought with distinction, with 16 receiving the Medal of Honor. The USCT regiments were precursors to the Buffalo Soldier units which fought in the American Indian Wars.