Western Canada consists of a series of progressively younger orogenic belts from the Archean Slave province westward to the present continental margin. Each belt was superimposed on the westernmost rim of its predecessor. With no sign of preliminary rifting, each cycle started with deposition of a continental terrace wedge. Each cycle then evolved through various styles of compression orogeny but was never terminated by continental collision. Thus the data indicate that there has been a western continental margin to Canada since Archean time–a margin that has been both passive and active but which was neither generated by rifting nor destroyed by continental collision. The pattern is similar farther to the south for middle Proterozoic to Holocene time, but is less clear for early Proterozoic time.