As the fifth president of the United States, James Monroe purchased Florida from Spain, extended the country's territory into the Pacific Northwest, helped control sectional tensions and asserted the primacy of the United States in the Western Hemisphere. His term lasted from 1817 to 1825.
Monroe's signal accomplishment was the formation of the Monroe Doctrine. In this policy, Monroe asserted that European colonization in the New World was over, and that any attempts to reconquer the newly independent nations of South and Central America would be opposed with force. He also promised not to intervene in European politics.
Even before he was president, Monroe played a large role in expanding the territory of the United States. In 1803, he assisted in the negotiations to purchase the Louisiana Territory from France. He continued this practice while in office. He supported the Treaty of 1818 with Great Britain, which allowed American settlers into the Pacific Northwest, and he purchased Florida from Spain while defining the country's western borders in the Treaty of 1819.
This increase in territory led to sectional tensions between the slave-holding South and the relatively free North, but Monroe and his allies in Congress calmed the tension with the Missouri Compromise of 1820. He also supported the colonization of Africa with freed slaves in Liberia. The grateful colonists named the country's capital, Monrovia, after him.