The fonds consist of diaries, photographs, scrapbooks, photographs albums and ephemera created by or about Canadian nursing sister Clare Gass (1887-1968). A diary and a photograph album chronicle Clare Gass's experiences as a nurse with the Canadian Army Medical Corps stationed in France and England during the First World War. The diary contains entries dated between 4 March 1915 to 31 December 1916 and also features an early appearance of the poem "In Flanders Field," written by John McCrae during the war upon the burial of a close friend. It is copied out in the diary entry for 30 October, nearly six weeks before its first publication in the magazine Punch on 8 December 1915. The diary originally had ephemeral material originally laid in, including newspaper clippings, manuscript notes and letters, one photograph, pencil drawings, and ten dried plant specimens. These have been removed from the diary for preservation purposes. Her photograph album from the First World War begins in April 2015 with photos of the nursing sisters assembled for inspection before deployment and the sea crossing to Europe. The photographs include depictions of soldiers and nursing sisters, oftentimes in their huts, and hospital interiors from multiple hospitals at which she worked and visited. It contains photographs from various postings in Etaples, Camiers, Cliveden (England) Boulogne, and Rhyl (Wales), as well as landscapes, historical sites, and other scenes from the surrounding areas that she toured, including a trip to Scotland. Leaves 13 and 14 of the photograph album also contain the text of “In Flanders Field.”

Loose photographs also document Gass’s wartime experiences in France, as well the hospital at St. Anne de Bellevue, Quebec, and Gass's transit duties in the Rockies in 1919. A series of photographs are from the visit of the Prince of Wales to Quebec October and November of 1919. Other loose photographs also depict wounded veterans, as well as personal photographs, including a portrait of Clare Gass at age 13.

Her childhood is also documented in the fonds by a photograph album containing photos from her years attending Edgehill School. The photos date chiefly between 1904 and 1905 and depict school exteriors, interiors, friends and classmates, as well as school activities such as Drill Class.

An additional folder contains material compiled by Gertrude Henderson, including letters to Clare Gass, some of her writings, and other ephemera, such as clippings noting Gass’s retirement, sketches, some of Gass’s poetry and stories, a memorial from King George to those who served in the war, and manuscript notes on Gass’s school and word record, including years and places that she was stationed. The folder also contains assorted later photographs of Gass.