This table provides a list of historical U.S. newspapers that are available online at no cost. Newspapers available for free through Google News Historical Archives and Newspaperarchives.com are listed individually as I identify them. Newspapers available through Chronicling America and state digitization projects are usually listed as a group. For instance, under "Wyoming" I have not listed every newspaper digitized in the project but simply described what is available.
Links to several dozen newspapers' sites, sortable by name and by city. A drop-down menu lets you choose which section of the paper the links go to, which is useful though it needs some updating.