Recommended Readings:

Becker, William and Wells, Samuel, Economics and World Power: An Assessment of American diplomacy since 1789, Columbia University Press, New York, 1984

Damiani, Brian P., Advocates of Empire: William McKinley, the Senate and American expansion, 1898 - 1899, Garland Publishers, New York, 1987

Dudden, Arthur, American empire in the Pacific: from trade to strategic balance, 1700 - 1922, Ashgate, 2004

Fredman, Lionel, The United States enters the Pacific, Angus and Robertson, Sydney, 1969

Garrison, Jim, America as empire: rogue leader or rouge power, Berret-Koehler Publishers, San Francisco, 2004

Greene, Theodore, American Imperialism in 1898, Heath, Boston, 1955

Guerra, Ramiro, The territorial expansion of the United States: at the expense of Spain and the Hispanic-American countries, University of America Press, Lanham, 2003

Hietala, Thomas, Manifest Design: American exceptionalism and Empire, Ithaca, London, 2003

Remini, Robert Vincent, Andrew Jackson and the course of American empire, 1767 - 1821, Harper and Row, New York, 1977

May, Ernest, American imperialism: A Speculative Essay, Atheneum, New York, 1968

Merk, Frederick, The Monroe Doctrine and American expansionism, 1843 - 1849, Knopf, New York, 1966

Owsley, Frank Lawrence, Filbusters and expansionists: Jeffersonian Manifest Destiny, University of Alabama Press, Tuscaloosa, 1997

Paterson, Thomas and Rabe, Stephen, Imperial Surge: the United States abroad, the 1890s -- early 1900s, Heath, Lexington, 1992

Thomson, James, Peter Stanley and John Perry (1981) East Asia in the American Mind and The Opening of Japan. Sentimental Imperialists. The American experience in East Asia. Harper & Row, New York, pp. 4-19, 61-79.
Van Alstyne, Richard, The American Empire: Its historical pattern and evolution, Routledge, London, 1960

Wayne, Morgan, America's Road to Empire: The War with Spain and Overseas Expansion, Wiley, New York, 1965

Articles

Merk, Frederick, Manifest Destiny and Mission in American History: A Reinterpretation, The American Historical Review, Vol. 69, No. 2. (Jan., 1964), pp. 479-480. 

Pratt, Julius, The Origin of “Manifest Destiny”, The American Historical Review, Vol. 32, No. 4. (Jul., 1927), pp. 795-798.

M. Consuelo Leon W., Foundations of the American Image of the Pacific, boundary 2, Vol. 21, No. 1, Asia/Pacific as Space of Cultural Production. (Spring, 1994), pp. 17-29.

Links:

http://www.nationmaster.com/encyclopedia/Philippines
Background information about the Philippines

http://www.boondocksnet.com/centennial/gildage.html
Directory of resources on U.S. history of the late nineteenth century just before the creation of an empire during and after the Spanish-American War of 1898.

http://www.mtholyoke.edu/acad/intrel/to1914.htm
An extensive site with original documents and other valuable links relating to American foreign policy 1898-1914. These links provide a good understanding of the discourses, which ultimately lead to the Spanish-American War and the American War in the Philippines.

http://www.boondocksnet.com/centennial/spanam.html 
‘The Spanish-American War’, with background papers elaborating on politics, human rights and the role of journalism, with several original newspaper articles and essays by members of the Anti-Imperialist League.

http://www.smplanet.com/imperialism/toc.html
‘An online-history of America: the age of imperialism’, on American expansionist policies which extended their political and economic influence around the globe.

http://www.cohums.ohio-state.edu/history/projects/McKinley/
‘The era of W. McKinley’, by K. Austin Kerr, Ohio State University, provides contemporary material, about the McKinley presidency, including the Spanish-American War.