John Quincy Adams
John Quincy Adams bagged the top spot as the smartest President in US history. With a spectacular IQ of 175, Adams had what it took to make significant changes. We should always remember his forward-thinking on the subjects of slavery and free speech. Still, even the eminent Adams was not as effective as he could have been. Despite his proficiency in seven languages and the great capacity of his mind, Adams prioritized daily skinny-dipping sessions over paying attention to the needs of the nation.