The local public library in Fayetteville, NY has a collection of 42,000 titles of sheet music, covering American popular song from the Civil War era to the 1980's. It includes political campaign songs, Broadway and Hollywood shows, folk, rock, jazz, country, and others.
Email librarian Laurie Heyboer lheyboer@fflib.org to inquire whether they have the title you are looking for.