To identify U.S. papers from a particular time and place, consult Chronicling America: Newspaper Directory at the Library of Congress. This draws on several older bibliographies:
Concrete information about a newspaper's ownership, circulation, and readership can be elusive. First, search for a book or article on the paper in which you are interested. Otherwise, consult a general directory of newspapers and periodicals for the period of interest:
Annual directories of U.S. newspapers:
For circulation figures for 20th-century papers, see Editor and publisher. International year book number. Firestone Oversize PN4700.E4q (covers 1938 to present).
To locate books on the history of a particular newspaper, do a keyword search in the Main Catalog for the name of the paper, e.g. "new york herald tribune"
The world's great dailies: profiles of fifty newspapers. John C. Merrill and Harold A. Fisher. New York: Hastings House, c1980.
Trustee Reading Room Reference (DR) PN4731 .M446
Very useful essays on 50 major papers, U.S. and foreign.
If Princeton does not hold the newspaper you need, you may be able to obtain microfilm of the paper through Interlibrary Loan. In particular, many newspapers are available on microfilm from the Center for Research Libraries, an organization of which Princeton is a member. CRL collects not only mainstream U.S. papers, but also U.S. ethnic papers (searchable by ethnic group in their online catalog) and foreign newspapers. There is a printed catalog of CRL's holdings as of 1978:
The Center for Research Libraries catalogue--newspapers. Chicago: The Center, 1978. RECAP Z6945 .xC533 1978
The Library of Congress, state archives and libraries, local historical societies, and some large public libraries have substantial collections of local U.S. newspapers, in print and in microfilm, often including titles available nowhere else. The New York Public Library also has a substantial collection of newspapers. Much of this material is not available through Interlibrary Loan, so you must travel to the archive or library to see the paper you need. To find out where you might find a specific newspaper, check Worldcat or one of the guides listed above.
A useful (but dated) guide to several important newspaper collections is:
Untapped sources: America's newspaper archives and histories. Prepared for the American Society of Newspaper Editors' Newspaper History Task Force by the Gannett Foundation Media Center at Columbia University in the City of New York; written by Jon Vanden Heuvel; edited by Craig LaMay and Martha FitzSimon. [New York: Columbia University; 1991.]
Firestone Z6951 .V26