15. George Washington
Source: Wikipedia.
He may not have been the smartest President, but he was the very first president of the United States. President Washington had no formal education and only had the education of an elementary school child, yet, according to recent studies and calculations based on his life and personality, Washington was an incredibly intelligent individual, having an IQ of 132, which makes total sense considering he was able to lead a nation -both politically and militarily- towards gaining its own independence.