I found some info that might be helpful to you:

Here's an ad for a book called David Stone In Sunset Valley, a history of the KSTP Barn Dance. (A.k.a. the Sunset Valley Barn Dance)

The New Hampshire Library of Traditional Music and Dance has the following book in its catalog:
Lair, John. 100 WLS BARN DANCE FAVORITES. Chicago: M. M. Cole Publishing Co., 1935. 95 pp.

This webpage called The History of WLS Radio contains a photo of the cover of a book called (as far as I can make out) "Favorite Mountain Ballads and Old-Time Songs [sung?] by Bradley Kincaid" which the caption describes as a "WLS/Sears Songbook from the late 1920's."

This webpage called Nashville Songwriters Hall Of Fame : Bradley Kincaid mentions a book called "My Favorite Mountain Ballads" published in April 1928 which sold about 110,000 copies.

One source tells me that the "WLS Barn Dance" started in 1924 and was renamed the "National Barn Dance" when NBC began carrying it in 1933.

The Library of Congress lists a book called "Favorite songs, KSTP Sunset valley barn dance" from 1943. It also has the John Lair book described above, on microfilm.