What was the Monroe Doctrine and Why was it important to the United States after the Civil War?
Monroe Doctrine, statement of United States policy on the activities and rights of European powers in the western hemisphere. It was made by President James Monroe in his seventh annual address to the Congress of the United States on December 2, 1823; it eventually became one of the foundations of U.S. policy in Latin America. Because it was not supported by congressional legislation or affirmed in international law, Monroe’s statement initially remained only a declaration of policy; its increasing use and popularity elevated it to a principle, specifically termed the Monroe Doctrine after the mid-1840s. As far as the United States was concerned, the Monroe Doctrine meant little until the 1840s, when presidents John Tyler and then James Polk used it to justify U.S. expansion. In 1845 Polk invoked the doctrine against British threats in California and Oregon, as Tyler had done in 1842 against French and British efforts to prevent the U.S. annexation of Texas. In 1848 Polk warned that Eu
