CHAPTER VIII. 
General Characteristics of the Great Plain of the Columbia , and Navigability of the 
Columbia River. 
In reference to the Cascade mountains, the geography of this whole range has been repre¬ 
sented very inaccurately on all existing maps. The region between the Cceur d’Alene and the 
Cascade mountains may be described as follows : 
It extends with an average of over 200 miles between these two ranges; and from the Blue mount¬ 
ains, at the sources of the John Day river, Umatilla, and the southern tributaries of the Wallah- 
Wallah river, to the Kootenaies mountains, north of Clark’s fork, is marked by the Columbia and 
its principal tributaries—Clark’s fork or Flathead, and Lewis or Snake river. The general 
course of the Columbia is north and south, with two large bends—one to the westward from Fort 
Okinakane, and the other to the eastward, approaching Wallah-Wallah. The Spokane river is the 
principal remaining tributary on the east, and the Yakima the most important one on the west of 
the river. The Yakima and its tributaries lead to the only two passes of the Cascades that can 
well be availed of for wagon roads, and one of which—the Snoqualme Pass—having two routes 
over the divide, will probably furnish a feasible railroad route. 
North of the Spokane river, and for a few miles south of it, the country is well timbered 
and well watered, with many fertile prairies and valleys. The valleys of the Coeur d’Alene and 
Spokane rivers, the valley extending from the Spokane to Colville, the Coeur d’Alene prairie, 
and the country generally between the Coeur d’Alene and Pend d’Oreille lakes, are well adapted 
to grazing and agriculture. The Flat Bow river, whose general course is parallel to that of the 
Flathead river, or Clark’s fork, makes a re-entering into our territory nearly to 48° 30', has much 
good land on its banks, and the country between it and the Flathead lake is generally prairie, the 
divide being low. One of the routes from the Flathead lake to the Pend d’Oreille lake is by the 
southern bend of the Flat Bow river. 
I have denominated the prairie region, between the Coeur d’Alene mountains and the Cas¬ 
cades, the Great Plain of the Columbia. The formation of the central and western portions is 
trap, and it presents great variety of surface and character, from fertile and well-watered valleys 
to desert sage plains, and from gently undulating waves of vegetation to basaltic columns, deep 
canons, and the various outcroppings observed in such formations. The Coeur d’Alene mount¬ 
ains are a vast mass of limestone, and the valleys on its western slope are rich and inviting. 
Thus, on the Kooskooskia there is a fine agricultural and grazing region, and in December Mr. 
Tinkham found the grass perfectly green, peas up, and flowers in blossom. So of the several 
tributaries flowing into the Coeur d’Alene lake. The St. Joseph’s, the most southern tributary, 
and which probably furnishes a route across the mountains better than the Coeur d’Alene or 
either of the Nez Perces trails, and which it is said can be made practicable for wagons at very 
small expense, has many large and extensive prairies, and the whole region westward to the 
route pursued by the main party is profusely watered, and well adapted to grazing. Indeed, for 
the entire region east of the Columbia, the country, with a few exceptions, as in the vicinity of 
the Grand Coulee, along certain portions of the Snake and Peluse rivers, may be called a good 
grazing country, and on no route pursued by voyageurs, by Indians, or by the parties of my 
exploration, were there long distances between water. The longest distance made was from the 
