Answer:
When Lincoln shared the draft of the Emancipation Proclamation with Secretary of State William H. Seward, the latter advised him to wait for a major victory before announcing it to the nation. Therefore, Lincoln announced the emancipation after the Battle of Antietam.
Step-by-step explanation:
The Emancipation Proclamation was an executive order issued on September 22, 1862 by President Lincoln abolishing slavery in the areas of the Confederate States of America, entering into force on January 1, 1863. Work on the project started in July. At the news of victory at Antietam, Lincoln signed the Proclamation on September 22 after consulting with members of the Cabinet, especially his Secretary of State William H. Seward.
At the time of its ratification, the Proclamation released a minimum number of slaves, but as the Union annexed the Confederate territories, this opened the way for the total abolition of slavery in American territory. Slavery became illegal through the approval of the 13th Constitutional Amendment, a fact that occurred in 1865.