Just discovered this digital archive of popular american sheet music.

http://digital.library.ucla.edu/apam

The UCLA Music Library's Archive of Popular American Music is a research collection covering the history of popular music in the United States from 1790 to the present. The collection, fully accessible at the item level through the UCLA Library Orion2 catalog, is one of the largest in the country, numbering almost 450,000 pieces of sheet music, anthologies, and arrangements for band and orchestra.

Very easy to search. I have already placed it in the links section of the Mudcat.

Roger in Baltimore