James Monroe was the fifth president of the United States, serving from 1817 to 1825. He was a key figure in the early history of the United States and is best known for the Monroe Doctrine, which warned European powers against further colonization or intervention in the Americas. Monroe also oversaw the acquisition of Florida from Spain and the Missouri Compromise, which sought to maintain a balance between free and slave states. He was a strong advocate for westward expansion and is often remembered for his presidency's emphasis on national unity and economic development.