Before 1865 the Constitution gave a president no power to abolish slavery in peacetime, with the three-fifths compromise, the fugitive slave clause and the Dred Scott decision treating enslaved people as property. Early in the war General Benjamin Butler declared escaped slaves contraband of war, a wartime seizure the administration backed. In the summer of 1862 Lincoln read a draft proclamation to his cabinet, and William Seward warned that issuing it amid defeats would look like a last shriek of retreat.

In August Lincoln answered Horace Greeley publicly that saving the Union was his paramount object, while the draft sat in his desk. After Antietam he issued the preliminary proclamation on September 22, giving the Confederacy 100 days, and quietly sent envoys to Louisiana, Tennessee and Arkansas offering to let them keep slavery if they rejoined. The final order of January 1, 1863 applied only to areas in rebellion, exempting loyal border states, Tennessee and occupied counties and parishes, because it rested on his war powers as commander in chief.

• Lincoln proposed a constitutional amendment for compensated emancipation phased in by 1900.
• The proclamation immediately freed roughly 25,000 to 75,000 people in occupied areas such as the Sea Islands.
• Nearly 200,000 Black men ultimately joined the Union ranks.
• News spread through networks such as the 4Ls, Lincoln’s Legal Loyal League.
• Copperhead backlash cost Republicans seats in 1862, while Manchester textile workers backed the Union through the cotton famine.