Chris,

A quick place to start is at:

   http://www.music.indiana.edu/music_resources/composer.html
   http://www.kanadas.com/music/composers.html
   http://www.hnh.com/qcomp.htm

Without having checked thoroughly, I'm sure most of the 20th century
composers listed were born earlier than mid-century, but you might find
some leads here.  I know there are some deserving names which are not on
these sites.

Dick Hihn