Imperialism By the middle of the 1890's the American western frontier was viewed by many as being "closed". This was seen as the fulfillment of the westward expansions started under the banner of "manifest destiny". The public perception of the "closing of the west", along with the philosophy of Social Darwinism, contributed to a desire for continued expansion of American lands and the spreading of American culture. The result was a shift in US foreign policy at the end of the 19th century from a reserved, homeland concerned republic to an active imperial power. The Spanish-American War The "USS Maine" pictured here in Havana Harbor, Cuba The Spanish-American war heralded the start of the era of American Imperialism. In the shadow of the expanding empires of Europe, an America that now stretched from sea to shining sea was desiring to still grow. Causes of the Spanish-American War: Cuban Revolution - The Spanish suppres...