Final answer:
Abraham Lincoln's issuance of the Emancipation Proclamation on January 1, 1863, marks one of his major achievements, transforming the Civil War's purpose and leading to the eventual abolition of slavery in the United States.
Step-by-step explanation:
The issuance of the Emancipation Proclamation on January 1, 1863 is the historic executive order declared that all slaves in Confederate-held territory were to be set free, which shifted the war objectives of the Civil War towards the abolition of slavery.
While the proclamation did not immediately free a single slave, it was a crucial step towards the eventual liberation and served as a precursor to the Thirteenth Amendment, which permanently abolished slavery in the United States.
The Emancipation Proclamation also allowed African Americans to serve in the Union Army and Navy, contributing significantly to the Union's war effort and ultimately helping to overpower the Confederacy.
Lincoln’s leadership during the Civil War, with acts such as the Emancipation Proclamation and delivering the iconic Gettysburg Address, not only maintained the Union but also laid the foundation for equality and freedom for all Americans.