In 1823, President James Monroe enunciated a policy that further separated Europe from the western hemisphere. In essence, his pronouncements sought to keep European powers from colonizing North, Central and South America. Any such effort in any part of the hemisphere would be considered "an unfriendly disposition toward the United States."
The general motivation for President Monroe's actions rested with thinkers from the American revolutionary era. However, the doctrine's specific origins came from a conflict between the United States and Russia over land settled in Alaska. In the midst of that 1821 conflict, Secretary of State John Quincy Adams developed the principle that European nations had no legal right to claim land in the western hemisphere. In short, a limited 19th century, Russian-U.S. conflict gave rise to a policy that lasted well into the 20th century, falling into disrepute during the anti-colonial struggles in Latin America and elsewhere.