meanwhile found pictures of the following books and added them to my CS discography at http://www.wirz.de/music/sandburg.htm

Carl Sandburg: The American Songbag.
A collection of 280 songs from all regions of the United States
Harcourt, Brace and Co., New York, 1927, 1970, 1990

and

Carl Sandburg's New American Songbag
New York Broadcast Music Co. 1950
(with 60% new songs not in the first American Songbag)