What important action did Abraham Lincoln take?

Abraham Lincoln is renowned for his pivotal role in the emancipation of enslaved people in the United States. The most significant action he took in this regard was issuing the Emancipation Proclamation in 1863, which declared that all enslaved people in Confederate-held territory were to be set free. This action not only aimed to weaken the Confederacy during the Civil War but also laid the groundwork for the eventual abolition of slavery throughout the nation with the 13th Amendment. Lincoln's insistence on preserving the Union while also advocating for freedom for enslaved individuals marks him as a key figure in American history related to civil rights and liberty.

In contrast, establishing National Parks is associated with later presidents and conservation efforts, while leading the US during the Great Depression pertains to Franklin D. Roosevelt. The signing of the Declaration of Independence was undertaken by Thomas Jefferson, not Lincoln, and occurred long before Lincoln's presidency.