Mission and History (American Memory from the Library of Congress)

The Library of Congress has built up an impressive resource collection for public use, and is still building. The above link takes you to the page that explains the project and gives an overview of its history:

American Memory provides free and open access through the Internet to written and spoken words, sound recordings, still and moving images, prints, maps, and sheet music that document the American experience. It is a digital record of American history and creativity. These materials, from the collections of the Library of Congress and other institutions, chronicle historical events, people, places, and ideas that continue to shape America, serving the public as a resource for education and lifelong learning...

Among the many other offerings at American Memory is a Today in History page at http://lcweb2.loc.gov/ammem/today/today.html.