A speech given by President Monroe to Congress, the Monroe Doctrine stated that Europe should not colonize or mettle in the affairs of the Americas. It promised the US’ neutrality in conflicts between Europe and its colonies unless the conflicts occurred in the Americas, in which case the US would see the act as hostile. It was later expanded, under President Grant, to bar the transfer of Western Hemisphere countries from one European country to another, and to allow the US intervention in the Americas.
". . . At the proposal of the Russian Imperial Government, made through the minister of the Emperor residing here, a full power and instructions have been transmitted to the minister of the United States at St. Petersburg to arrange by amicable negotiation the respective rights and interests of the two nations on the northwest coast of this continent. A similar proposal has been made by His Imperial Majesty to the Government of Great Britain, which has likewise been acceded to. The Government of the United States has been desirous by this friendly proceeding of manifesting the great value which they have invariably attached to the friendship of the Emperor and their solicitude to cultivate the best understanding with his Government. In the discussions to which this interest has given rise and in the arrangements by which they may terminate the occasion has been judged proper for asserting, as a principle in which the rights and interests of the United States are involved, that the American continents, by the free and independent condition which they have assumed and maintain, are henceforth not to be considered as subjects for future colonization by any European powers. . ."