Elihu Stewart 
Down the Mackenzie and up the Yukon in 1906 [EPUB ebook] 

The area drained by the Mackenzie River is of vast extent, covering something over 450, 000 square miles. Its principal tributaries flow from the west; they consist of the Athabaska, the Peace, the Liard and the Nahanni with many others of smaller size. To illustrate by comparison the size of the Mackenzie basin with that of some other streams, it is only necessary to say that the area of the St. Lawrence basin above the City of Montreal is about 310, 000 square miles, while that of the Saskatchewan, including its two branches, is only 159, 000 square miles; so that the Mackenzie basin exceeds that of the St. Lawrence above Montreal, including that of all the great lakes by 140, 000 square miles, and is nearly three times as great in extent as the basin of the Saskatchewan, including both the north and south branches of that great river.