The Emancipation Proclamation was a presidential proclamation and executive order issued by President Abraham Lincoln on January 1, 1863. In a single stroke, it changed the federal legal status of more than 3 million enslaved persons in the designated areas of the South from "slave" to "free". It had the practical effect that as soon as a slave escaped the control of the Confederate government, by running away or through advances of federal troops, the slave became legally free. Eventually it reached and liberated all of the designated slaves. It was issued as a war measure during the American Civil War, directed to all of the areas in rebellion and all segments of the executive branch (including the Army and Navy) of the United States.

The Proclamation was issued in two parts. The first part, issued on September 22, 1862, was a preliminary announcement outlining the intent of the second part, which officially went into effect 100 days later on January 1, 1863, during the second year of the Civil War. It was Abraham Lincoln's declaration that all slaves would be permanently freed in all areas of the Confederacy that had not already returned to federal control by January 1863. The ten affected states were individually named in the second part (South Carolina, Mississippi, Florida, Alabama, Georgia, Louisiana, Texas, Virginia, Arkansas, North Carolina). Not included were the Union slave states of Maryland, Delaware, Missouri and Kentucky. Also not named was the state of Tennessee, in which a Union-controlled military government had already been set up, based in the capital, Nashville. Specific exemptions were stated for areas also under Union control on January 1, 1863, namely 48 counties that would soon become West Virginia, seven other named counties of Virginia including Berkeley and Hampshire counties, which were soon added to West Virginia, New Orleans and 13 named parishes nearby.

Union-occupied areas of the Confederate states where the proclamation was put into immediate effect by local commanders included Winchester, Virginia, Corinth, Mississippi, the Sea Islands along the coasts of the Carolinas and Georgia, Key West, Florida, and Port Royal, South Carolina.

Source: WikiPedia