ROCKY MOUNTAINS, THE, are the principal division of that vast system of highlands occupying the western third of the United States and a narrower belt in western Canada. Standing between the great continental plains on the east and the region of elevated basins and plateaux stretching from Nevada to central British Columbia on the west, they constitute the back bone of the continent, as well as a major topographical feature of the entire globe.
At the south, the Rockies first become prominent in northern New Mexico where there are elevations above 13,00o feet. Thence they sweep for 2,200 m. through the United States and Canada to the Yukon. In Canada, for 450 m. they form the boundary between Alberta and British Columbia, where they are known as the "Canadian Rockies." Their greatest width and elevation are attained in Utah and Colorado. Here the system of ranges is 300 m. across. In Colorado there are 46 summits surpassing 14,00o ft., Mt. Elbert (14,419 ft.) being the highest of the system and the second highest peak in the United States. Colorado con tains about 254 mountains between 13,00o and 14,00o feet. North-west of Colorado breadth and elevation diminish, until at the Canadian boundary the ranges are less than ioo m. wide, with few elevations exceeding 9,500 feet.
From Colorado almost to the Peace river in British Columbia, the Rockies carry the watershed of the continent-the continental divide. But this does not mean that they present a continuous chain of great peaks. On the contrary the zone of uplift is rather a vast complex of separate ranges, interrupted at places by wide gaps of lofty rolling plateaux.
In the United States, the crest-line of the Rocky Mountains definitely breaks down at two places-the plateaux of Yellow stone Park and Great Divide Basin in southern Wyoming (6o m.
by ioo m.). The three divisions thus produced-north, central and southern-may be taken as a convenient basis of description.
They correspond approximately with the States of Montana, Wyoming and Colorado (with which Utah is associated). The elevations of these major breaks or passes are as follows : in southern Arizona, 4,615 ft. (Southern Pac. R.R.) ; in New
Mexico, Campbell's Pass, 7,25o ft. (Santa Fe R.R.) ; in Great Divide Basin, 7,102 ft. (at Creston, Union Pacific R.R.) ; in Yellowstone Park plateaux, about 8,30o ft.
by 20 m.) and the Sangre de Cristo range (4o m. by io m.) in the central part of the State. In the south-western corner the Elk, San Miguel (with the spectacular Lizard Head, 13,156 ft.), Needle and other groups, form an incredibly wild and rugged mass of peaks.
The Wasatch mountains of central Utah, overlooking the great basin for ioo m., present abrupt ranges, of which Mt. Delano (12,24o ft.) is the highest. Associated with the Wasatch moun tains is the Uinta group (15o m. by 25 m.), of which Kings Peak (13, Soo f t.) is loftiest. Five others exceed 13,000 feet.
Reverting to the continental divide of the western part of Wyoming, the important uplift of the Wind River Range is next in order, north-west of Great Divide Basin. It is about 1 oo m. long, the core being upwards of 13,000 ft. in elevation and sending out long lateral ridges between which remarkable canyons occur.