Who was President of the United States during the 1861-1865 American Civil War?

Explanation

Abraham Lincoln was the 16th President of the United State and the first Republican president. He served during the American Civil War from 1861 until his assassination in 1865, and helped abolish slavery. Abraham Lincoln was killed during a play at Ford's Theatre in Washington D.C. on 14 April 1865. The killer was the Shakespearian actor John Wilkes Both. Lincoln thus become the first American president to be asasssinated whilst in office.