Geologist Arthur Philemon Coleman [1852–1939] explored in the area in 1908. Coleman wrote:

[At the Foot of Mount Robson] By walking a hundred yards from our camp into the valley Mount Robson came into view during the rare intervals when the clouds drifted away, disclosing an imposing dome of white rising eight thousand feet above our valley, the lower part banded with courses of rock. Immediately behind our little grove a half-mile of glacier flowed, separating us from the cliffs of the Rearguard, one of the subordinate peaks, which reached a height of about nine thousand feet.

From his vantage on Mumm Peak during the 1911 Alpine Club of Canada–Smithsonian Robson Expedition, Arthur Oliver Wheeler [1860–1945] described the rugged ridge running from the centre of Mount Robson’s north-east face. “The ridge ends in a semi-detached rock mass, aptly named by Coleman ‘Rearguard.’”

Paleontologist Charles Doolittle Walcott [1850–1927] explored in the Mount Robson area in 1912:

Directly above Blue Glacier a point of rock was named by Dr. Coleman “The Helmet,” and the great black mountain in the center, which he called the “Rearguard,” is now given the Indian name of Iyatunga (Black Rock) (note: name approved by the Geographical Board of Canada, December, 1912)

“Iyatunga” is no longer official. No one seems to have used it except Walcott.