One of the best places to start research is in the Five-College Library Catalog . All books are listed by their AUTHORS, TITLES, and SUBJECTS, and you can also use the KEYWORD function to search.
If you have an exact citation, use AUTHOR or TITLE searching.
To identify books on particular topics, try KEYWORD searching, but keep in mind that, in itself, such a search is not likely to yield a complete, or completely relevant, list of locally-owned books on any particular topic. Start your KEYWORD search by typing in a common language characterization of your topic, say "revolutionary war loyalists", then select titles from the resulting list that interest you, note which official subject headings are assigned to those titles, then click on them to do a more thorough SUBJECT search.
SUBJECT searching, as such, requires that you use the exact words or phrases libraries have chosen to describe your topic; for example, libraries list books about loyalists during the Revolution under "American loyalists -- History" and broader coverage is under the heading "United States -- History -- Revolution -- Social Aspects"; note the way the subject headings are subdivided. Ask at the Reference Desk if you're not sure what words or phrases to use.
America's Historical Newspapers (1690-1980)
Searchable archive of American newspapers including Early American Newspapers (1690-1922) and Hispanic American Newspapers (1808-1980).
America: History & Life (1964 to present)
Covers the world's scholarly literature on the history and culture of the United States and Canada.
American Periodicals (1740-1940)
Digitized reproductions of more than 1,100 18th and 19th century newspapers and periodicals.
Historical Abstracts (1955 to present)
Scholarly literature about world history since 1450 (excluding the United States and Canada).
American National Biography
Information on over 17,400 men and women.
Gale Virtual Reference Library
70 reference e-books, including multivolume works like the Encyclopedia of Religion, American Decades, and more.
Print-format reference works
Dictionary of American History. N.Y., Scribner's, 2003. 3rd ed. 10 vols.
The basic encyclopedia of U.S. history. Brief articles about places, events, topics, and people, most with little bibliographies. (Ref E 174 D52 2003)
The Blackwell Encyclopedia of the American Revolution. Cambridge MA, Blackwell, 1991.
Solid, 10- to 15-page essays (with lots of citations) on major background topics, events, and concepts related to the Revolution. (Ref E 208 B635 1991)
The American Revolution, An Encyclopedia. N.Y., Garland, 1993. 2 vols.
Some short and some longer entries, most with references to further readings. (Ref E 208 A433 1993)
Encyclopedia of the New American Nation, the Emergence of the United States, 1754-1829. N.Y., Thomson Gale, 2006. 3 vols.
Entries on topics, events, places and people of significance, most with brief bibliographies. (Ref E 301 E53 2006)
Revolutionary America, 1763-1789, a Bibliography. Washington DC, Library of Congress, 1984. 2 vols.
A massive listing of secondary sources, a little old now, but it can be updated with online finding tools. (Ref E 208 G47 1984)
Early American Imprints, Series I (1639-1800)
Books, pamphlets, broadsides and other imprints listed in the renowned bibliography by Charles Evans.
Early American Imprints. Series II, Shaw-Shoemaker (1801-1819)
Books, pamphlets, broadsides and other imprints listed in the distinguished bibliography by Ralph R. Shaw and Richard H. Shoemaker.
American Memory Project: A rich -- and somewhat unpredictable -- collection of digitized documents, photographs, maps, and much more, all drawn from the vast collections of the Library of Congress. A federally sponsored project to reflect American history and culture.
Gilder Lehrman Institute of American History: Digitized documents and images from the collections of the New York Historical Society.
American Archives, Documents of the American Revolution 1774-1776: A digitized version of a 9-volume compilation of pamphlets, booklets, newspaper articles. etc., originally published in the early-mid 19th century.
Fold3, Historical Military Records: Formerly Footnote.com; includes millions of digitized records of Revolutionary War pensions, service records, etc.
Boston 1775: A blog with hundreds of links and references to texts about Revolutionary War activity in and around Boston.
The American Colonist's Library, A Treasury of Primary Documents: Hundreds of links to documents, mounted by a self-identified "conservative" blogger; a hodge-podge, but full of fascinating material.
Links to style manuals...the Library's Citing Sources page.