From 1951 through 1954, Mulloy supervised the investigation of an 8000-year-old bison kill site near Laramie.
In 1955, Mulloy and Dr. H. Marie Wormington, then Director of the Colorado Museum of Natural History and long acknowledged doyenne of North American Plains Archaeology, served as co-directors of archaeological survey work in Alberta, Canada conducted under the auspices of the Glenbow Museum Foundation.