John Gunn arrived from Scotland in 1911 to manage the 4X Bakery in Calgary, but soon left to concentrate on his burgeoning dairy farm. In 1929, he commissioned Victor Dionne, a contractor from the United States, to build this barn to house his dairy herd at the Gunn farm, which stood just east of what is now the Calgary International Airport.
During his career as a dairy farmer, Gunn was asked to supply milk to the Banff Springs Hotel during King George VI and Queen Elizabeth's stay, and to the Royal Train during Princess Elizabeth and Prince Philip's visit to Calgary. Gunn died in 1957, and in 1978 his daughter, Margaret Dallas Gunn, donated the barn and $50,000 to Heritage Park for its relocation and restoration. Gunn's Dairy Barn is used by the Park as a food service and entertaining facility.