Abraham Lincoln ( February 12 , 1809 â `` April 15 , 1865 ) was the 16th President of the United States . He served as president from 1861 to 1865 , during the American Civil War . Abraham Lincoln ( February 12 , 1809 â `` April 15 , 1865 ) served as the 16th President of the United States from March 1861 until his assassination in April 1865 .