I don't know if this is the entire collection of Lomax recordings of Jean Ritchie, but there sure are a lot of them at Berea Colleage:

http://digital.berea.edu/cdm/search/collection/p16020coll7

Many Lomax recordings of Ritchie also available here:

http://research.culturalequity.org/get-audio-ix.do?ix=recording&id=10401&idType=sessionId&sortBy=abc

-Joe-