Original: James Buchanan , Jr. ( April 23 , 1791 -- June 1 , 1868 ) was the 15th President of the United States from 1857 -- 1861 and the last to be born in the 18th century .
Simplified: James Buchanan ( April 23 , 1791 - June 1 , 1868 ) was the 15th President of the United States .