Original: William McKinley , Jr. ( January 29 , 1843 September 14 , 1901 ) was the 25th President of the United States , and the last veteran of the American Civil War to be elected .
Simplified: William McKinley ( January 29 , 1843 -- September 14 , 1901 ) was the 25th President of the United States , from 1897 until his assassination in 1901 .