The area commonly known as the Coeur d'Alene district (although for purposes of record and administration it has been divided into a number of local mining districts) is situated, so far as its productive part is concerned in Shoshone County, in that narrow portion of Idaho which extends northward between the States of Washington and Montana to the international boundary. It lies almost entirely upon the western slope of Coeur d'Alene Mountains, a broad and rather complex member of the North American Cordillera.