Since the end of Reconstruction, the American political system has demonstrated its ability to adapt to changing domestic and foreign policy requirements. Indeed, in the years directly following Reconstruction, attention was necessarily focused on domestic matters.
A shift from an agrarian economy to one based largely on industry created a new sets of needs and expectations for the American population.
A political movement called Progressivism responded to these needs by calling for reform: monopolies were broken-up; corruption was addressed; the government provided more services, laws were enacted to protect women, children, and the large immigrant population; food and drug safety was seen to; and regulations regarding sanitation and hygiene were established.
Many of these reforms necessitated the establishment of governmental institutions such as the Food and Drug Administration and the Department of Labor. Many of these institutions are still in operation today.
With the beginning of the United States’ involvement in World War I, attention was redirected to foreign matters. Americans became increasingly involved in world affairs, not only through their involvement in the war efforts but also through imperialism (which had begun earlier and had increased rapidly with the acquisition of Guam, the Philippines, and Puerto Rico in 1898). These actions required new governmental institutions or changes to existing organizations.
A similar shift was seen with the Great Depression (focus on domestic affairs) and World War II (focus on foreign policy), and this see-sawing continues to the present day. One of the strengths of the organization of the American government is its ability to evolve.
Federal laws and institutions can be changed according to the demands of the economy (for example tax reform and government bail-outs of troubled sectors of the economy), societal values (debates over parental rights and gay marriage, to name but two of the relevant issues), and foreign interests.
Hispanic Division, Library of Congress. “The World of 1898: The Spanish-American War.” http://www.loc.gov/rr/hispanic/1898/intro.html.
Swann, John P. “History of the FDA.” Adapted from Kurian, George, ed. A Historical Guide to the U.S. Government (New York: Oxford University Press, 1998). U.S. Food and Drug Administration. http://www.fda.gov/oc/history/historyoffda/default.htm.
United States Department of Labor. “History at the Department of Labor: Departmental Timeline.” http://www.dol.gov/oasam/programs/history/dpt.htm.
 Columbia Encyclopedia, 6th ed., s.v. “Progessivism.”
 John P. Swann, “History of the FDA,” adapted from George Kurian, ed., A Historical Guide to the U.S. Government (New York: Oxford University Press, 1998), U.S. Food and Drug Administration, http://www.fda.gov/oc/history/historyoffda/default.htm.
 United States Department of Labor, “History at the Department of Labor: Departmental Timeline,” http://www.dol.gov/oasam/programs/history/dpt.htm.
 Hispanic Division, Library of Congress, “The World of 1898: The Spanish-American War,” http://www.loc.gov/rr/hispanic/1898/intro.html.