7. James Monroe
Monroe was the fifth President of the United States and is probably best known for signing the Monroe Doctrine. At the time when most Latin American colonies of were gaining their independence from their European colonizers, Monroe wanted to ensure that these independent colonies would remain free from European intervention and considered separate, independent nations. The doctrine would go on to become one of the most defining moments in U.S. foreign policy history and would impact the world for more than a century later.
He also oversaw the Missouri Compromise, which ended a long running dispute whether or not the newly formed state of Missouri would be a slave state. Before that, there were 22 states in the U.S., 11 free, 11 slave-states. If Missouri was decided to be one or the other, it would upset the balance, so congress finally decided to make it a slave-state and form a new state, Maine, as a free. But the most important thing to come out of the Compromise was that slavery was permanently banned anywhere north and/or west of Missouri, marking the first time that congress passed a law in regards to slavery.