The Rosa Breithaupt Clark Architectural Collection is the result of an endowment made by Herbert Spencer Clark in 1982 in memory of his late wife, Rosa Breithaupt Hewetson Clark, formerly of Kitchener. Included in purchases made through this endowment are exemplary treatises from the sixteenth to the twentieth century supportive of the School of Architecture's cultural history emphasis.

Awards made in 1987 and 1990 by the Social Sciences and Humanities Research Council (SSHRC) of Canada under their programme supporting the development of specialized research programmes enabled the collections to grow significantly. The first grant was dedicated to the purchase of landmark titles in the history and theory of architecture. Since the discourse of architecture ultimately looks back to the Roman writer, Vitruvius, it was appropriate that the first acquisition using these funds was a rare edition of a Vitruvian treatise printed in 1536.

The second of the SSHRC grants was awarded in 1990 specifically to support the collection in an area of critical importance: architectural developments in Northern Europe and on the North American frontier which have a profound effect on architectural theory and urban development in Canada.

A third award made by SSHRC allowed the Library to purchase The Dictionary of Architecture issued by the Architectural Publication Society (1853-1892), described as a monument to nineteenth-century scholarship.

The William Dendy Library consists of more than 3,500 books and 2,500 periodical issues. For the most part, the collection focuses on the history of architecture, but other topics, such as music and literature, are featured as well.