Northern Prairie Wildlife Research Center
Lewis and Clark, Maxmillian and other early explorers left us some excellent descriptions of relative distribution of canids they saw in North Dakota during the early 1800's
Early explorers recognized what they thought were two species of wolves - one was larger and common, the other considerably smaller and rare. We can only speculate, but it is likely that the smaller, rarer species was the coyote.
In addition, they noted that red foxes were not uncommon and they documented some cross fox and some silver fox. Cross and silver fox are genetic recessive color variations of the red fox, and both variations can occur in the same litter depending on the genetic composition of the parents. Further, these explorers saw large numbers of swift fox in North Dakota.
Over time, canid distribution changed dramatically. Plains wolves were eliminated, allowing coyote populations to expand, and likely reducing fox distribution. In the mid-1900s, intense hunting trapping and poisoning significantly reduced coyote numbers, allowing red fox to expand.