Series consists of William Dendy's personal architectural slide collection depicting architecture, urban spaces, and landscapes. The majority of the collection, consisting of approximately 17,550 slides, is dedicated to Canadian architectural heritage. Slides from regions of the United States of America (ca. 7,000 slides), various Western European countries with a focus on England, as well as parts of Central and South America and the Caribbean are also included.

Roughly eighty percent of the slides were taken by Dendy in person. The remaining slides consist of commercially produced slides or reproductions of plans, maps, photographs, architectural drawings, paintings, etc. from books or archival collections where Dendy conducted research. Many of the reproduction slides consist of historical records in the the public domain and were likely taken by Dendy. Reproduction sources are often included on corresponding slide mounts.