The president of the United States during the Civil War was Abraham Lincoln. He served as the 16th president from 1861 until his assassination in 1865. Lincoln led the country through the Civil War, working to preserve the Union and playing a major role in the abolition of slavery. His presidency began shortly before the war started, and he was in office throughout the entire conflict until his death in April 1865, just days after the Confederate surrender at Appomattox Court House