Margaret Calder began her career at the Alexander Turnbull Library. She subsequently worked in research libraries in London and for a significant period at the Mitchell Library in Sydney.
While at the Mitchell Library she became responsible for the Pictures Collection, sparking an interest in images as a vital part of historical research. This interest continues and makes the work of the Cartoon Archive of special interest.
Margaret Calder returned to New Zealand in 1988 to the position of Assistant Chief Librarian before assuming the position of Chief Librarian of the Alexander Turnbull Library on the retirement of Jim Traue. She retired in 2007.