Title: Monroe Doctrine Centennial half dollar
Content:  militarily and most European powers ignored it, considering it beneath their dignity even to respond to such a proclamation. When several European powers dispatched men to settle land in the Guianas in the 1830s, the United States did not issue a formal protest. The Mexican–American War of 1846–1848 (and the resulting Mexican Cession) increased Latin American suspicions over the doctrine, as many south of the border felt that the American purpose in warning European powers to keep out was to acquire the land for itself. Nevertheless, the Monroe Doctrine became an important part of United States foreign policy in the second half of the 19th and into the 20th century.
Title: Latin America–United States relations
Content:  The 1823 Monroe doctrine, which began the United States' policy of isolationism, deemed it necessary for the United States to refrain from entering into European affairs but protect nations in the Western hemisphere from foreign military intervention, and warned against the establishment of any additional European colonies in Latin America. Despite this, European interventions continued to occur in American countries with the tacit or explicit support of the United States. These interventions include the re-establishment of British rule over the Falkland Islands in 1833, the French naval blockade of Argentine ports between 1839 and 1840, the Anglo-French blockade of the River Plate from 1845 to 1850, the failed Spanish invasion of the Dominican Republic between 1861 and 1865, the French intervention in Mexico between 1862 and 1865, and the establishment of British crown control over the Mosquito Coast in Nicaragua and of the Guayana Essequiba in Venezuela in 1855.
Title: America's Backyard
Content:  mercantilistic Spain which wanted to benefit its home economy at the expense of the South Americans. In light of all of this, President James Monroe proposed the Monroe Doctrine on December 2, 1823. The Doctrine stated that any further efforts by European countries to colonize land or interfere with states in the Americas would be viewed by the United States of America as acts of aggression requiring US intervention and asserted that the Western Hemisphere was not to be further colonized by European countries, and that the United States would not interfere with existing European colonies nor in the internal concerns 
Title: Monroe Doctrine Centennial half dollar
Content:  In the early 1820s, the United States deemed two matters untoward interference by European powers in its zone of influence. The first was the Russian Ukase of 1821, asserting exclusive territorial and trading rights along much of what is today Canada's Pacific coast. The United States considered this area to be part of the Oregon Country and hoped to eventually gain control of it. The second was possible European threats against the Latin American nations, newly independent from Spain. United States officials feared that a Quadruple Alliance of Prussia, Austria, Russia, and France would restore Spain to power in the Americas. British foreign minister George Canning was concerned that in the 
Title: Decolonization of the Americas
Content:  Great Britain and the United States were rivals for influence in the newly independent sovereign nations. As a result of the successful revolutions which established so many new independent nations, United States President James Monroe and the Secretary of State John Quincy Adams drafted the Monroe Doctrine. It stated that the United States would not tolerate any European interference in the Western Hemisphere. This measure ostensibly was taken in order to safeguard the newfound liberties of these new countries, but it was also taken as a precautionary measure against the intrusion of European states. Since the United States was a newly founded nation, it lacked the capacity to prevent other European powers from interfering, for that the United States looked for Britain's help and support to execute the Monroe Doctrine into action. Great Britain's trade with Latin America greatly expanded during the revolutionary period, which until then was restricted due to Spanish mercantilist trade policies. British pressure was sufficient to prevent Spain from attempting any serious reassertion of its control over its lost colonies.
Title: Monroe Doctrine
Content:  the European powers outside of the Americas, despite the fact that the European countries controlled much more of the Americas than the U.S. herself. Hamilton expected that the United States would become the dominant power in the New World and would, in the future, act as an intermediary between the European powers and any new countries blossoming near the U.S. A note from James Madison (Thomas Jefferson's Secretary of State and a future president) to the U.S. ambassador to Spain, expressed the American federal government’s opposition to further territorial acquisition by European powers. Madison's sentiment might have been meaningless because, as was noted before, the European powers held much more territory in comparison to the territory held 
Title: Francisco García Calderón Rey
Content:  to Latin America affect them in the negative light. He explains how, though there are connections to European countries who also pose a threat (namely Germany), North America, through the Monroe Doctrine, is trying to control the area for itself. By intervening with Latin American foreign policies, the States did not allow other countries to trade with Latin America, giving the Americans 30% control over the exports of Latin America. Calderón also described the situations with Cuba and Puerto Rico, which the Americans claimed to be dealing with but wound up annexing. He also uses the annexation of Texas, the buying of land along Panama to build the canal 
Title: José Joaquim Almeida
Content:  South America, shunned formal recognition for fear of a major conflict with Spain and its European allies and through the Secretary of State John Quincy Adams faced a negotiation with the Spanish Minister Luis de Adams y Onis in the territory of Florida and parts of Texas. In this negotiation, in the form of incessant correspondence, Ambassador Onis constantly protested what he saw as U.S. efforts to destabilize the Spanish colonies by allowing fleets of "pirate" working from Baltimore and New Orleans against the colonies' traffic. Monroe decided to pressure the district judges to refuse safe harbor to the pirates safe in 
Title: Monroe Doctrine
Content:  to support their fellow Americas nation as Monroe had stated should be done for collective security against European colonial powers. In 1842, U.S. President John Tyler applied the Monroe Doctrine to Hawaii and warned Britain not to interfere there. This began the process of annexing Hawaii to the U.S. On December 2, 1845, U.S. President James Polk announced that the principle of the Monroe Doctrine should be strictly enforced, reinterpreting it to argue that no European nation should interfere with the American western expansion ("Manifest Destiny").  In 1861, Dominican military commander and royalist politician Pedro Santana signed a pact with 
Title: James Monroe
Content:  he feared that France or the Holy Alliance might seek to establish control over the former Spanish possessions. On December 2, 1823, in his annual message to Congress, Monroe articulated what became known as the Monroe Doctrine. He first reiterated the traditional U.S. policy of neutrality with regard to European wars and conflicts. He then declared that the United States would not accept the recolonization of any country by its former European master, though he also avowed non-interference with existing European colonies in the Americas. Finally, he stated that European countries should no longer consider the Western Hemisphere open to new colonization, a jab aimed primarily at Russia, which was attempting to expand its colony on the northern Pacific Coast.

Question: who warned europe to stay out of the americas?
Answer: Monroe Doctrine.
Roosevelt Corollary.