The sixth president of the United States was James Monroe, who served from 1817 to 1825. He was a Founding Father and the last president of the Virginia dynasty. He is best known for his foreign policy, which became known as the Monroe Doctrine. This doctrine declared that the United States would not interfere in European affairs and that any attempt by a European power to colonize or interfere with the affairs of the Americas would be seen as an act of aggression.