Approximately twenty thousand years ago, continental glaciers covered almost all of Canada and the northern United States. Although the term "Ice Age" sounds very harsh and frigid, some science suggests there was less variation in temperature between the seasons than the present day. During this time, the region was home to mammoth, giant bison, ground sloth, and camels. People were not in this era until the very end of the Ice Age; 10,000 to 12,000 years ago.
You may want to read more about the Ice Age and Kansas: