From where the river skirts the base of the Blue Mountains its surroundings are less forbidding.  Much of the country is fertile, but its canyon is everywhere deep and almost inaccessible.  Steamers make their way up as far as Lewiston, a hundred and fifty miles, and receive cargoes of wheat at different points through chutes that extend down from the tops of the bluffs.  But though the Hudson’s Bay Company navigated the north fork to its sources, they depended altogether on pack animals for the transportation of supplies and furs between the Columbia and Fort Hall on the head of the south fork, which shows how desperately unmanageable a river it must be.

A few miles above the mouth of the Snake the Yakima, which drains a considerable portion of the Cascade Range, enters from the northwest.  It is about a hundred and fifty miles long, but carries comparatively little water, a great part of what it sets out with from the base of the mountains being consumed in irrigated fields and meadows in passing through the settlements along its course, and by evaporation on the parched desert plains.  The grand flood of the Columbia, now from half a mile to a mile wide, sweeps on to the westward, holding a nearly direct course until it reaches the mouth of the Willamette, where it turns to the northward and flows fifty miles along the main valley between the Coast and Cascade Ranges ere it again resumes its westward course to the sea.  In all its course from the mouth of the Yakima to the sea, a distance of three hundred miles, the only considerable affluent from the northward is the Cowlitz, which heads in the glaciers of Mount Rainier.

From the south and east it receives the Walla-Walla and Umatilla, rather short and dreary-looking streams, though the plains they pass through have proved fertile, and their upper tributaries in the Blue Mountains, shaded with tall pines, firs, spruces, and the beautiful Oregon larch (Larix brevifolia), lead into a delightful region.  The John Day River also heads in the Blue Mountains, and flows into the Columbia sixty miles below the mouth of the Umatilla.  Its valley is in great part fertile, and is noted for the interesting fossils discovered in it by Professor Condon in sections cut by the river through the overlying lava beds.

The Deschutes River comes in from the south about twenty miles below the John Day.  It is a large, boisterous stream, draining the eastern slope of the Cascade Range for nearly two hundred miles, and from the great number of falls on the main trunk, as well as on its many mountain tributaries, well deserves its name.  It enters the Columbia with a grand roar of falls and rapids, and at times seems almost to rival the main stream in the volume of water it carries.  Near the mouth of the Deschutes are the Falls of the Columbia, where the river passes a rough bar of lava.  The descent is not great, but the immense volume of water makes a grand display.  During the flood season the falls are obliterated and skillful boatmen pass over them in safety; while the Dalles, some six or eight miles below, may be passed during low water but are utterly impassable in flood time.  At the Dalles the vast river is jammed together into a long, narrow slot of unknown depth cut sheer down in the basalt.