Nanaimo Bars are indeed a Canadian classic dessert originating from none other than Nanaimo, BC.
The bar originated in Ladysmith south of Nanaimo in the early 1950s. Mabel Jenkins, a local housewife from Cowichan Bay, submitted the recipe to the annual Ladysmith and Cowichan Women's Institute Cookbook. This cookbook was sold in the early 1950s in the region as a fundraiser. It became popular in many of the province's households, especially in company towns, and was sold in many of the coffee shops on Nanaimo's Commercial Street. Tourists in the region, especially US tourists on pleasure boats came to refer to these as "Nanaimo Bars". In Nanaimo and points south to Duncan, however, these were originally referred to as Mabel bars, or W.I. bars. The earliest confirmed printed copy of the recipe using the name "Nanaimo Bars" appears in a publication entitled His/Her Favourite Recipes, Compiled by the Women's Association of the Brechin United Church (1957), with the recipe submitted by Joy Wilgress, a Baltimore, Maryland native (p.52). (The Brechin United Church is in the north side of Nanaimo.) This recipe also is reprinted in Kim Blank's book Sex, Life Itself, and the Original Nanaimo Bar Recipe (Umberto Press, 1999, pp.127-29).
In 1954 the recipe "Mable's Squares" (p.84) was published in "The Country Woman's Favorite" by the Upper Gloucester Women's Institute (New Brunswick). The recipe was submitted by Mrs. Harold Payne, the daughter of Mable (Knowles) Scott (1883-1957). The ingredient list, quantities, and assembly steps closely match the recipe found on the City of Nanaimo web site.
The first printing of recipes featuring Nanaimo Bar ingredients is found in the 1952 Women's Auxiliary to the Nanaimo Hospital Cookbook. They are referred to as the Chocolate Square or the Chocolate Slice. Some say the first use of the name Nanaimo Bar was in an Edith Adams cookbook printed in 1953.
Other unconfirmed references date the bars back to the 1930s, when it was said to be known locally as "chocolate fridge cake".Some New Yorkers claim that it originated in New York, and refer to them as "New York Slices".However, Tim Horton's coffee shops in New York sell them as "Nanaimo Bars". One modern reference even refers to the bars existing in nineteenth century Nanaimo.