The Chronicling America project has digitized many of America's historic newspapers from 1836-1922. The images are free online and are searchable and browsable. Chronicling America is sponsored jointly by the National Endowment for the Humanities and the Library of Congress and has digitized newspapers from all 50 states.
Chronicling America: Historic American Newspapers (LOC)
Chronicling America: Historic American Newspapers (LOC)