The Cordilleran orogen, with an evolution that has spanned the entire Phanerozoic, is one of the longest lived orogenic belts on the planet. A reason for its long history is that since at least Cambrian time the Re has been a large region underlain by oceanic lithosphere to the west of continental North America, and such continent-ocean lithospheric boundaries are tectonically unstable. Interaction between these two types of lithosphere resulted in intermittent tectonic activity during Paleozoic time, and nearly continuous tectonic activity during the Mesozoic and Cenozoic. Because Pacific oceanic plates are still present west of North America, the Cordilleran orogen continues to evolve. Plateboundary interactions along the western boundary of North America have included diverse types of convergent, divergent, and transform activity as well as combinations of these plateboundary interactions. Fortunately, the preservation of a large tract of Mesozoic and Cenozoic oceanic lithosphere west of North America enables the evolution of Pacific Basin plates to be reconstructed for Cenozoic time and, with less certainty, back to middle Mesozoic time (Engebretson and othe Rs, 1985; Stock and Molnar, 1988). Such reconstructions permit correlation between continental geology and lithospheric plate interactions to a degree uncommon in most post-Paleozoic orogens, and provide a testing ground for relating oceanic plate tectonics to continental deformation and evolution.