The Canadian Rockies form the most easterly ranges of the Cordilleran system for a distance of more than 1 050 miles, from the Yukon border south into central Montana. They are bounded on the east by the Interior Plains and to the west by the Rocky Mountain Trench. The main deformation occurred during the Eocene, resulting in a system of stacked thrust plates which are restricted to the sedimentary section and do not involve the crystalline basement rocks. More than 100 miles of shortening in the sediments occurred as a result of this deformation.Exploration in this structural belt has resulted in an important oil- and gas- producing province, with the major reserves located in the southern Foothills. The vast amount of information that has been accumulated in the course of this exploration through surface mapping, drilling, and geophysical work has provided excellent structural detail over a large part of the area.Prospective structures are difficult to locate, and they require careful integration of all available geological and geophysical control. Reflection and refraction seismic methods have had considerable success in locating many of the presently producing fields and have provided information that is fundamental to our understanding of this complex structural belt.