What important action did Abraham Lincoln take during his presidency?

The Emancipation Proclamation, issued by Abraham Lincoln in 1863, was a pivotal action during his presidency as it declared the freedom of all enslaved people in Confederate-held territory. This executive order represented a significant shift in the American landscape, both morally and legally. It transformed the Civil War from a battle for the Union into a fight for freedom, giving it a moral imperative that resonated deeply throughout the nation and garnered support from abolitionists.

By taking this significant step, Lincoln not only aimed to undermine the Confederacy's capacity to sustain its war effort, relying heavily on enslaved labor, but he also set a precedent for future policies aimed at civil rights and equality. This action paved the way for the eventual passage of the Thirteenth Amendment, which abolished slavery throughout the United States.

In contrast, the other options do not reflect actions taken by Lincoln or are historically inaccurate in the context of his presidency. The Federal Reserve was established in 1913, long after Lincoln's time, and the Spanish-American War occurred in 1898. While the Homestead Act was signed during Lincoln’s administration and promoted westward expansion, it does not carry the same revolutionary impact on civil rights as the Emancipation Proclamation.