CHAPTER Vi. 
Railroad Practicability of the Rocky and Coeur d’ Alene Mountains.—Description of the 
ranges and of the several passes. 
In determining the route through the Rocky mountains, regard must be had to the difficulties of 
approach as well as to the difficulties in the pass itself. Before considering the question, it 
will first be necessary to show the route through the Coeur d’Alene mountains. 
The Coeur d’Alene mountains may be regarded as extending from Snake river to Clark’s fork, 
and as covering from two to three degrees of longitude. Clark’s fork separating it from a range 
still farther north, called the Kootenaies mountains, has its source in the Rocky mountains in two 
principal branches—one flowing from the south, called the Bitter Root river, and the other 
flowing from the north, and called the Flathead river. These rivers separate the Coeur d’Alene 
and Kootenaies mountains from the Rocky mountains, and—with the exception of a mountain 
spur running down towards their point of junction, giving, however, a good pass from the one 
valley to the other—they form a continuous valley extending along the western base of the Rocky 
mountains from 45° 30 of N. latitude to far north into British territory. To the south, however, 
at the headwaters of the Bitter Root, of the Snake, and the three forks of the Missouri, the 
Cceur d’Alene unites with the main chain of the Rocky mountains. 
There are at least four passes in the Coeur d’Alene mountains, well known to the aborigines: 
the pass of Clark’s fork, the Coeur d’Alene pass by the Coeur d’Alene mission, the northern 
Nez Perces trail, and the southern Nez Perces trail. The northern Nez Perces trail is the route 
of Lewis and Clark, and was not examined. The three other passes have been carefully 
examined by me. There is said, however, to be a fifth trail between the Cceur d’Alene and 
northern Nez Perces trails, more practicable for wagons than any of the others. This has been 
explored by Lieutenant Mullan, but his report has not been received. 
The southern Nez Perces trail leads from the southwest fork of the St. Mary’s river, connect- 
ing, by a tolerably direct route, St. Mary’s valley with Wallah-Wallah. For 120 miles it passes 
over wooded mountains, dropping at times into valleys, and, crossing them, ascends the spurs and 
hills again. Its elevation rarely if ever falls so low as 3,000 feet, and sometimes reaches as high 
as 8,000 feet—an estimate, the barometer having been cached at the ;height of 7,250 feet. In 
the month of December, when, with considerable detention and difficulty, Mr. Tinkham crossed 
the mountains on snow-shoes, the snow was generally about three feet deep, sometimes six feet, 
and in a single instance, as near as could be ascertained, ten feet deep. The average depth of 
the snow for the whole 120 miles was a little less than two feet. Tributaries of the Koos-koos-kia 
head near the sources of the southwest fork of the St. Mary’s river, and offer the only possible 
chance of getting through the Bitter Root mountain. This direction is by the Koos-koos-kia. 
A tunnel will be required at the divide separating the two streams. The Koos-koos-kia was 
crossed near its head, at an elevation of 3,760 feet; its valley in this place is narrow and dark, 
with steep, rocky and wooded hills enclosing it. It has the same character where it unites 
with the Clearwater river after leaving the mountain. Between these two points the river has 
not been examined. The northern Nez Perces trail is very much of the same character, and 
does not come into competition fora route. ‘The Coeur d’Alene Pass may be briefly described 
as a pass formed by two streams flowing in opposite directions from two lakes almost half a 
mile apart. 'The western lake is about 700 feet above the eastern. The two valleys, though 
