On December 2, 1823, President James Monroe gave his 7th State of the Union address before Congress, using the occasion to advance what would later become known as the Monroe Doctrine. After a string of former Spanish colonies in the Americas declared their independence, Monroe said the United States would oppose further predation in the region from the European empires to preserve the newly emancipated states. As American power exploded during the 19th and early 20th centuries, the Monroe Doctrine evolved and increasingly came to mean Washington's opposition to any potentially hostile foreign power establishing itself in the Americas. With...