America's Historical Newspapers (1690 to 1922) provides access to scanned images from newspapers from all 50 U.S. states.
Newspapers.com provides access to articles from thousands of newspapers from the 1700s -2000s.
19th Century US Newspapers provides access to approximately 500 U.S. newspapers, published between 1800 and 1900.
African American Newspapers: The 19th Century provides the full text of articles from the following newspapers: Freedom's Journal, The Colored American, The North Star, The National Era, Provincial Freeman, Frederick Douglass Paper, and The Christian Recorder. Coverage begins in 1827 but varies by title.
African-American Newspapers (1827-1998) provides full-text access to over 350 newspapers from more than 35 states.
Hispanic American Newspapers, 1808-1980 provides full-text access to hundreds of Spanish-language newspapers.
Japanese-American Relocation Camp Newspapers is a collection of 25 newspapers which document life in the camps.
KKK Newspapers provides access to articles from local, regional, and national newspapers published by Klan organizations and by sympathetic publishers across the U.S. during the 1920s. It also includes the voices from several anti-Klan newspapers.
Chronicling America is a joint project of the Library of Congress and the National Endowment for the Humanities. Currently, you can search and view pages from the newspapers of around 30 states. The ultimate goal of this project is to have every state and U.S. territory represented in this digital archive. Coverage is 1836 to 1922 but varies by title.
Proquest Historical Newspapers provides access to scanned images from major U.S. newspapers: Atlanta Constitution (1868-1984); Baltimore Sun (1837-1992); Chicago Tribune(1849-1994); Los Angeles Times (1881-1994); The New York Times (1851-2014); The Wall Street Journal (1889-2000); The Washington Post (1877-2001). These titles can be searched simultaneously or individually.
Proquest Historical Newspapers: Black Newspapers provides access to scanned images from Atlanta Daily World (1931-2003); Baltimore Afro-American (1893-1988); Los Angeles Sentinel (1934-2005); New York Amsterdam News (1922-1993); Norfolk Journal and Guide(1921-2003); Pittsburgh Courier (1911-2002); the Cleveland Call and Post (1934-1991); and the Chicago Defender (1910 - 1975). These titles can be searched simultaneously or individually.
The Library has access to two newspaper data sets that are particularly appropriate for text mining:
From the record, click on the online option. This will take you to the Duke Digital Repository where the data sets reside.
Another possible source is Readers' Guide Retrospective, 1890-1982, which indexes popular magazines from this time period. This database, however, does not contain full-text articles, so your searches are limited to citations and broad subject headings.
An example citation: