The influential leader during the American Civil War was President Abraham Lincoln, who served as the 16th President of the United States from 1861 to 1865. Lincoln was pivotal in preserving the Union during this tumultuous period and is best remembered for his efforts to abolish slavery, culminating in the Emancipation Proclamation of 1863. His leadership encompassed both military strategies and legislative initiatives, such as the passage of the Thirteenth Amendment, which permanently abolished slavery. Lincoln's skillful oratory, including the Gettysburg Address, further solidified his legacy as a profound and steadfast leader committed to equality and liberty for all Americans.