Any edition published prior to 1923 in USA is in the public domain.  I believe the EU copyright is only 50 years.  Notation, editorial matter published after 1922 in USA most likely is still protected.  In the case of early radio broadcasts, no copyright exists unless so stated at the time of broadcast.  Thus Librivox for example records content explicitly in the public domain with the caveat the public domain of one country is not necessarily the same as in the reader / listener country.  For me the 50 year rule would be best to compensate the author / creator and give the public access to all materials older. 

Gordon Snedecor in Portland, Oregon