This is postmarked 1956.  It was published by Blackburn News Agency.  The company was located on Boone Street, started in 1945 by Joseph D. Blackburn and his wife, both former school teachers in Charlotte.  In 1960, they were servicing over 200 newsstands in the area with paperbacks and, obviously, postcards (Kingsport Times-News).  It was printed by Curt Teich in Chicago.

Blackburn had a series of postcards of Kingsport.  This is noted as B-27.