12 COAL RESOURCES OF THE YUKON. [no. 218. 
east the basin is not outlined by any mountain chain, and the tributa- 
ries of the Yukon interlock irregularly with those of the Liard, which 
is confluent to the Mackenzie, and with the Stikine, flowing into the 
Pacific. The chief of the Yukon tributaries are the Koyukuk, the 
Tanana, the Porcupine, the White, the Pelly, and the Lewes. The 
last two rivers named unite to form the Yukon proper. The general 
trend of the upper drainage channels of the basin is to the north and 
northwest to the point where the Yukon touches the Arctic Circle; 
at this point the river makes a right-angled bend to the southwest and 
continues to hold this general course to the head of the delta. 
The catchment basin of the Yukon, which includes about one-quarter 
of the area of Alaska, lies for the most part in what has been called 
the Central" Plateau region — that great dissected upland area lying 
between the Rocky Mountain system on one hand and the Pacific 
mountain system on the other. In its upper course the Yukon Valley 
is incised to a depth varying from 2,000 to 3,000 feet, and has a width 
of from 2 to 3 miles. Near the international boundary the valley 
contracts to a width ranging from one-half mile to a mile, and 150 
miles below it broadens out again and merges into that extensive low- 
land known as the Yukon Flats. Through this lowland the Yukon 
finds its way by many intricate channels, which in places spread out 
to a width of 10 or even 15 miles. Below the flats the river flows 
through a constricted part of its valley, known as the Ramparts, from 
which it emerges near the mouth of the Tanana. For about 600 miles 
below the Ramparts the valley is broad, and the river meanders over a 
wide flood plain. At the head of the delta the Yukon separates into 
a number of widely diverging distributaries. 
Since the Yukon is one of the great rivers of the world and is navi- 
gable by steamer for over 2,000 miles, and in both winter and summer 
is the great natural highway of travel through the interior of Alaska, 
development has been more rapid and exploration has been made more 
complete along it than in most other parts of Alaska. 
By the middle of the nineteenth century the Russian and Hudson 
Bay fur traders had already established themselves on the Yukon, 
and up to the time of discovery of gold, in the early eighties, this 
trade was the only thing that brought white men into the country. 
After the discovery of gold many prospectors made their way into the 
region, and at the time of the finding of the Klondike placers, in 1896, 
mining was carried on at several points on and near the Yukon, and 
camps were established at Rampart and Circle in Alaska and at Forty- 
mile on the Canadian side. At that time one or two small steamers 
brought all the supplies from St. Michael for the mining camps and 
trading posts. The influx of population brought about by the Klon- 
dike discoveries led to a phenomenal development of the transporta- 
a Brooks, Alfred H., Geography of Alaska: Prof. Paper U. S. Geol. Survey No. — . 
