Final answer:
Abraham Lincoln made a significant contribution to United States history by delivering the Emancipation Proclamation Speech in 1863.
Step-by-step explanation:
One individual who made a significant contribution to United States history is Abraham Lincoln. His contribution was significant because he delivered the Emancipation Proclamation Speech in 1863, which declared that all slaves in Confederate territory were to be set free. This was a turning point in the Civil War because it shifted the focus of the war to ending slavery and gaining freedom for enslaved African Americans. The Emancipation Proclamation also paved the way for the passage of the 13th Amendment, which officially abolished slavery in the United States.