According to their Mission Statement, the ADG’s Guild provides…
a variety of levels of access and support, thereby making collections available for reference and research to the staff and members of the Art Directors Guild and the community at large.
… A wide variety of print and photograph materials are available to provide visual references for Production Design research. Materials on Guild history and the history and practice of Art Direction and Production Design in film, TV and theater are also held on-site.
[It’s unclear how non-guild members obtain access, but it should be worth contacting them.]
For more information or access to the ADG Archives:
Rosemarie Knopka, Archivist