A mysterious First Nations society migrated to the Canadian Plains and eventually settled there, new archaeological findings suggest.

Siksika (Blackfoot) oral history has spoken of a peaceful group of people who broke from a tribe further south and who settled in the Blackfoot territory. The artefacts recently recovered at the site (about 120 kilometres east of Calgary) support these stories.

What's more, it appears its unknown inhabitants journeyed up from what is now north-central United States, to reach their eventual settlement site - the only one of its kind in the region.

http://www.tc.umn.edu/~bakk0029/Old_Copper/OC_Sec_3.HTML
1961
Trace Element and Metallographic Studies of Prehistoric Copper Artifacts in North America: A Review. In Lake Superior Copper and the Indians: Miscellaneous Studies of Great Lakes Prehistory, Anthropological Papers, Museum of Anthropology, University of Michigan, no. 17, edited by James B. Griffin, pages 151-176.

This source includes a review of trace element analysis and metallurgical studies of North American native copper. Bastian concludes that trace element analyses up to that time were crude, contradictory and of no use in determining copper sources. These analyses have been superseded by recent work (e.g. Rapp et al. 1980; 1984; 1989) utilizing more powerful modern assay techniques and computer driven statistical correlation techniques.

1963
Prehistoric copper mining in Isle Royale National Park, Michigan. M.S. Thesis, University of Michigan.

Berg, Ernest L.

1945
Stone and Metallic Materials Used by Ancient Indians of Minnesota in the Making of Artifacts. The Minnesota Archaeologist 11(1):4-17.

Berg examines various raw materials utilized locally in prehistory for the manufacture of artifacts. He also gives a few notes on the sources and properties of native copper.

probably to service some of those prehistoric copper mines of Canada.

Highly doubtful, the area they settled in does not contain copper deposits, a more likely scenario is that they were simply looking for "greener pastures".

Edward Sheriff Curtis photographed all of the major Native American Tribes, west of the Mississippi, with several grants from J.P. Morgan, beginning in the late 1880's through the Great Depression. His goal was to document "The Vanishing Race" as they were prior to the many developments, which cost Native Americans their precious homelands. The North American Indian consisted of 20 volumes of photogravures and text, documenting Native American customs, including interviews with many Native Americans who describe in their own words the heritage of their tribes. Each volume was accompanied by a portfolio of large Photogravures, relating to the tribes depicted in the volumes. There are 1510 volume size and 722 portfolio size photogravure plates in the entire collection.

Copper Photogravure Plates are produced utilizing the process of etching glass photographic positives, onto copper plates. Like the original photogravures printed by Curtis, The Curtis Collection photogravure prints are hand printed, utilizing the original copper plate and a Brand press.