Lake McArthur (JANHI) is in the Kootenay Land District of British Columbia.

[2] It is easily the deepest lake in the park, and its depth gives it a deep blue colour.

It goes on, "A couple of miles away is McArthur's Lake, a sapphire gem, located above the tree line, and with a huge glacier, fed on the precipitous heights of Mount Biddle, terminating in the water, where it breaks off in huge icebergs.

[3] McArthur was mapping the land through which the Canadian Pacific Railway line would travel, and he and his assistant T. Riley had to climb up to summits carrying heavy equipment so McArthur could take photographs and make measurements for his survey.

[7] Lake McArthur may be accessed via an 8-kilometre (5.0 mi) circuit hike from Le Relais Day Shelter in Yoho Park.