National Jukebox from the Library of Congress

The Library of Congress has put online over 10,000 recordings made between 1910 and 1925 that cover all eras of US history.  Here is the outline of the recordings, here is the search engine, music from the Civil War eras, old frontier and lyrical music.  For more information you can go to their blog that details how to integrate the Library of Congress resources into your classroom.