Tertiary sources are excellent starting points! They consist of information synthesized from primary and secondary sources. These resources give you succinct overviews of your topic, explain scholarly arguments, point out interesting questions, and refer you to especially key sources.
Start with these subject encyclopedias and branch out as needed.
Print encyclopedias and dictionaries are located on the first floor of Collins Library.
Dictionary of American History by 
Encyclopedia of American History by 
Encyclopedia of American Cultural and Intellectual History by 
Encyclopedia of the United States in the Nineteenth Century by 
Encyclopedia of American Social History by 
Social History of the United States by 
Encyclopedia of African American Culture and History by 
Encyclopedia of African American Culture and History by 
New Dictionary of the History of Ideas by 
American National Biography by 
African American Lives by 
Notable American Women by 