Reconstruction Era: Post-U.S. Civil War military control of Mississippi ends and it is readmitted to the Union.

The Reconstruction era was a period in US history that followed the American Civil War (1861–1865) and was dominated by the legal, social, and political challenges of the abolition of slavery and reintegration of the former Confederate States into the United States. Three amendments were added to the United States Constitution to grant citizenship and equal civil rights to the newly freed slaves. To circumvent these, former Confederate states imposed poll taxes and literacy tests and engaged in terrorism to intimidate and control African Americans and discourage or prevent them from voting.

The American Civil War was a civil war in the United States between the Union and the Confederacy, which was formed in 1861 by states that had seceded from the Union. The central conflict leading to war was a dispute over whether slavery should be permitted to expand into the western territories, leading to more slave states, or be prohibited from doing so, which many believed would place slavery on a course of ultimate extinction.

Mississippi is a state in the Southeastern and Deep South regions of the United States. It borders Tennessee to the north, Alabama to the east, the Gulf of Mexico to the south, Louisiana to the southwest, and Arkansas to the northwest. Mississippi's western boundary is largely defined by the Mississippi River, or its historical course. Mississippi is the 32nd largest by area and 35th-most populous of the 50 U.S. states and has the lowest per-capita income. Jackson is both the state's capital and largest city. Greater Jackson is the state's most populous metropolitan area, with a population of 591,978 in 2020. Other major cities include Gulfport, Southaven, Hattiesburg, Biloxi, Olive Branch, Tupelo, Meridian, and Greenville.

The Union was the central government of the United States during the American Civil War. Its civilian and military forces resisted the Confederacy's attempt to secede following the election of Abraham Lincoln as president of the United States. Lincoln's administration asserted the permanency of the federal government and the continuity of the United States Constitution.