William McKinley was shot after giving a speech in Buffalo, New York, on September 6, 1901.
He was shaking hands with people passing through a receiving line when a man fired two shots into his chest at point-blank range.
Doctors had expected McKinley to recover but gangrene then set in around the bullet wounds.
McKinley died on September 14, 1901, six months after opening his second term.
He was succeeded by Vice President Theodore Roosevelt.
Leon F. Czolgosz, an unemployed, 28-year-old Detroit resident, admitted to the shooting.
Czolgosz was found guilty at trial and put to death in the electric chair on October 29, 1901.
