The unsatisfactory condition of the nomenclature at present applied to the larger topographic features of North America is illustrated by the fact that to the north of the United States-Canadian boundary the term _Rocky Mountains_ is much more restricted than is the custom in the United States. In Canada this name is applied to the most easterly of the ranges or chains of the Pacific cordillera. This difference in the significance of the name referred to on the opposite sides of the international boundary is unfortunate, but is due in large part to our ignorance of the geography and geology not only immediately along the boundary line, but generally throughout the rugged region of the northwest portion of the continent. One of the most important geographic features in the central part of the United States is the presence in Wyoming of a broad, generally flat, region known as the Laramie plateau (plains) and its extension westward across nearly the entire width of the Rocky Mountains. The general elevation of these "plains" is about 7,000 feet, or approximately 1,000 feet greater than that of the western border of the Great plateaus. The Laramie plateau and country to the west having a similar topography, furnished a convenient pass for the Union Pacific, the oldest of the transcontinental railroads, and divides the Rocky Mountain belt into two portions, which may be termed in a general way the northern and southern Rocky Mountains respectively. To the north of the Union Pacific Railroad there are several important mountain groups, termed collectively the Stony Mountains by Lewis and Clark in the report of their bold explorations across the continent in 1804, but not generally used since that time. This name has recently been revived by J. W. Powell as a convenient term by which to designate this large division of the Rocky Mountain belt, but unfortunately is not recognised and has no significance to the north of the international boundary. What the natural limitations of the Stony Mountains may be in Canada remains to be determined.