The Prairies cover southern Alberta, Saskatchewan, and Manitoba, from the foothills of the Rockies to within 170 kilometres of the southwestern border of Ontario.

Like the adjoining Boreal Plains to the north, glaciers have largely flattened the

land here, leaving behind a thick layer of dark, humus-rich topsoil (called chernozem, or black earth) that has made the Prairies very fertile, and created Canada’s most extensive agricultural region. But it is mainly because of farming that the once ubiquitous grasslands, the northern limit of the Great Plains of North America, are now mostly gone. A sample of what once was can be seen in the only National Park on the Prairies, aptly named Grasslands, in southwestern Saskatchewan. Here, in the two separate “blocks” that make up the park, can be found not only fields of wind-swept blue grama, spear, wheat and other grasses, but also landforms typical of the parts of ecozone that lie in Saskatchewan and Alberta – most notably coulees (deep ravines) and buttes (flat-topped, isolated hills). Outstanding examples of both exist in Frenchman River Valley, which was sculpted by glaciers some 10,000 years ago.

At the same time that the glaciers were shaping this valley, the western end of the Prairies, the Manitoba Lowlands, was covered by Lake Agassiz, the largest glacial lake in North