The document discusses the shift in U.S. foreign policy from isolationism to imperialism in the late 19th century, as the country began expanding its influence in the Pacific. It describes how Commodore Perry opened trade with Japan in 1853, the U.S. purchase of Alaska from Russia in 1867, and the annexation of Hawaii and Samoa to control refueling areas in the Pacific. It also mentions the development of spheres of influence in China and the Boxer Rebellion that resulted from foreign involvement in China.