The narrow strip of prairie covered by the Foothills Erratics Train extends along the eastern flanks of the Rocky Mountains of Alberta and northern Montana to the International Border. The boulders of the Foothills Erratics Train consist of pink and purple Lower Cambrian shallow marine quartzite and conglomeratic quartzite, that are not native to this region of Alberta. These rocks only occur within the Gog Group that is exposed in the Tonquin Valley in the Rocky Mountains of central western Alberta. Their specific source has been identified as being near Mount Edith Cavell in Jasper National Park. Lying on prairie to the east of the Rocky Mountains, the larger glacial erratics of the Foothills Erratics Train are visible for a considerable distance across the prairie and likely served as a prominent landmark for Indigenous people.