American Imperialism and the Open Door Policy.
At the end of the Civil War, America was becoming increasingly outward looking as exports of both manufactured goods and agricultural goods shot up. Many Americans believed that United States had to expand or explore after the close of the western frontier. The U.S. was bursting with a new sense of power and nationalism, generated by the booming increase in population, wealth, and industrial production. Many Americans thought that overseas markets might provide a safety valve to relieve such pressures as; labor violence and agrarian unrest.
Other forces also stimulated overseas expansion. The "Yellow Press" of Joseph Pulitzer and William Randolph Hearst wetted the Americans taste for excitement aboard. Missionaries, inspired by books like the Reverend Josiah Strong's Our Country: Its Possible Future and Its Present Crisis, looked overseas for new fields to till. Americans wanted to spread their religion and their civilization to the "backward" peoples. At the same time aggressive Americans like Theodore Roosevelt and Henry Cabot Lodge were interpreting Darwinism to mean that the earth belonged to the strong and fit.
If America was to survive in the competition of modern nation-states, perhaps it too, would have to become an imperial power. The development of a new steel navy would eventually help America become an imperial power. Captain Alfred Thayer Mahan's book, argued that the control of the sea was the key to world dominance. Americans joined in the demand for a mightier Navy and for an American built isthmian canal between the Atlantic and the Pacific Oceans, (Panama Canal). .
After looking back, the United States of America turned to a policy of imperialsm because of economic expansion at home, the amazing industrialization of America in the half century following the Civil War, the nations sudden emergence of being a world power, and national pride.