What was one important thing that Abraham Lincoln did?

Abraham Lincoln played a pivotal role in the fight against slavery in the United States, most notably through the issuance of the Emancipation Proclamation in 1863. This executive order declared that all slaves in the Confederate states were to be freed. This action not only changed the status of enslaved individuals but also redefined the purpose of the Civil War, transforming it into a struggle for freedom as well as the preservation of the Union. In addition to the Emancipation Proclamation, Lincoln's leadership and commitment to the abolition of slavery ultimately contributed to the passage of the Thirteenth Amendment, which formally abolished slavery in the United States.

While Lincoln did indeed give the Gettysburg Address, which is a significant speech emphasizing the principles of human equality and national unity, it is his actions toward emancipation that are most directly associated with freeing the slaves. The other choices either describe events that did not involve Lincoln or pertain to historical timelines and contexts unrelated to his presidency.