American Memory: Historical Collections for the National Digital Library
Primary source and archival materials covering topics such as art and architecture, performing arts, technology and applied sciences.

Chronicling America: Historic American Newspapers
This site allows you to search and view US newspaper pages from 1880-1923 and find information about American newspapers published between 1690-present.

Digital Public Library of America (DPLA)
Brings together the riches of America's libraries, archives, and museums, and makes them freely available to the world.

Umbra Search: African American HistoryA digital collection of African American materials from over 1,000 libraries and archives across the country.