In 1983 Princess Diana and Prince Charles were on a Canadian tour, visting Edmonton, Alberta where they attended a Barbecue where attendees were requested to wear "Klondike Era" outfits. Diana chose this gown, which had been designed by Linda Mattock, and had been used previously in the ITV mini-series, Lillie, about the life of Lillie Langry. Though the dress was used, it had to be altered to fit Diana's frame. She also chose not to use the Victorian undergarments which give it its beutiful shape showcased in Lillie.
Eventually this dress was sold by Bonham’s, and has been on display several times. It currently is on display at the Queen Mary in Long Beach, California at an exhibit called Diana: Legacy of a Princess.
To see an extensive history about this dress, visit this fantastic site.