expansionism in the late 1800’s, including but not limited to, the closing of the frontier, the open door thesis, and the panic of 1893. Although, the idea of manifest destiny along with the theory of preclusive imperialism blend together in order to justify American expansion while at the same time, the Monroe Doctrine made it illegal for countries to interfere with American affairs. Combined together, the Monroe Doctrine, preclusive imperialism, and manifest destiny are great ideas that can be used to condone the United States reasons for expansionism in the 19th