The ideas expressed in George Washington's Farewell Address emphasize the importance of avoiding entangling alliances and maintaining neutrality in foreign affairs. A development in the early 1800s that best represented the continuation of these ideas would be the Monroe Doctrine of 1823.
The Monroe Doctrine stated that the Americas should be closed to further European colonization and that any attempt by European powers to interfere in the affairs of the Western Hemisphere would be seen as a hostile act against the United States. This doctrine reflected Washington's sentiment by asserting a policy of avoiding entanglement in European conflicts and maintaining a form of isolationism in American foreign relations.