Athabasca, a river, lake, and region on the eastern slope of the Canadian Rockies. The river rises in the Rocky Mountains of Alberta, near the sources of the Saskatchewan, and flows in a tortuous, northerly direction into Lake Athabasca, whence its waters find their way ultimately through the Mackenzie River to the Arctic Ocean. Its length is about 600 miles, equal to that of the Seine and the Thames combined. Lake Athabasca is about 200 miles in length with an extreme width of thirty-five miles. It is comparable in size to Lake Ontario. The district of that name was a quadrangular territory, comprising a quarter of a million square miles, lying east of British Columbia and extending from the sixtieth parallel of north latitude to Alberta and Saskatchewan. The population in 1901 was 6,615. In 1905 it was divided between the two provinces of Alberta and Saskatchewan.