Four albumen prints on cream-toned card mounts document the Northern Rocky Mountains of Montana along the U.S.–Canada international boundary, produced during a USGS geological survey in the summer of 1901 by geologist and photographer Bailey Willis (1857–1949). Willis was lecturing on geology at Johns Hopkins University between 1895 and 1902 and was simultaneously serving as head of the Division of Areal Geology of the USGS. His landmark 1902 paper, "Stratigraphy and Structure, Lewis and Livingston Ranges, Montana," published in the Bulletin of the Geological Society of America, drew directly on fieldwork conducted during these expeditions. Willis identified Chief Mountain as a thrust klippe, recognizing that Precambrian basement rocks were faulted up and over Cretaceous strata along the Lewis Overthrust.

The four views present distinct vantage points: Chief Mountain and its satellite peaks seen from the west, its flat-topped Precambrian limestone summit rising above rocky talus slopes; a wide panoramic view across a still lake with the mountain's distinctive silhouette visible far across the tree-lined shore; the summit of Mt. Gould with the south end of Grinnell Glacier visible from Mt. Grinnell, showing tiered snowfields and exposed cliff faces; and a close-range view taken from the Canadian side of the international divide at longitude 114°03'28", looking southeastward into the United States, with a survey monument just visible on the ridge. Chief Mountain summits at 9,085 feet and is described geologically as a klippe structure, an isolated erosional remnant that has tectonically shifted from its original location. Chief Mountain, called Ninaistako by the Blackfeet people, is considered sacred by them and by other Native American and First Nations peoples.

For people of the Blackfoot Confederacy, which includes tribes in the U.S. and Canada, Chief Mountain has helped define their territory for millennia, its prominence and visibility providing guidance and a landmark for travelers. The photographs carry exceptional documentary weight as primary survey records made before Glacier National Park was established in 1910, capturing the landscape in a state of scientific discovery.

Each mount is inscribed in ink on the reverse with the subject description, location, date, and the signature "Bailey Willis"; dates read July 1901 and August 1901 respectively. Mounts measure approximately 8 x 10 inches.