This work investigates the fossilized plant life of the Cretaceous and Tertiary periods found in British Columbia and the Northwest Territories. John William Dawson, a prominent Canadian geologist and paleontologist, draws upon extensive fieldwork and existing geological surveys to present his findings. The book aims to classify and describe the various flora discovered, providing insights into the ancient ecosystems and geological history of these regions. Dawson's analysis is grounded in the scientific methods of 19th-century paleobotany, focusing on the morphology and stratigraphy of fossil specimens.

As a foundational work in Canadian paleobotany, Dawson's "On the Cretaceous and Tertiary Floras of British Columbia and the North-West Territory" is recognized for its detailed cataloging of fossil plant life from a critical period in Earth's history. The book provides essential data for understanding the paleoecology and geological evolution of Western Canada. Its scientific rigor and comprehensive approach established a benchmark for subsequent research in the field. The work remains a valuable reference for paleontologists and geologists studying the region's ancient flora.