The Rocky Mountain Front: Where the Mountains Begin

The Rocky Mountain Front in Montana is one of the most ecologically significant landforms in North America and one of the most visually abrupt. This is where the Great Plains, which have been building since the last ice age across a thousand miles of gradually rising grassland, run directly into the wall of the Rockies with no transitional terrain between them. You are driving across flat or gently rolling prairie and then, within a few miles, the mountains are there, vertical and fully formed, with no foothills as warning.

The uplift that produced this wall is ancient, roughly sixty to seventy-five million years old, the result of thrust faulting in which older rock has been pushed eastward over younger rock in a geologic process that is visible in the tilted strata of the leading ranges. The geology you see on the Front is not the normal sequence. Old is on top, young is below.

The ecological significance comes from the fact that the Rocky Mountain Front is one of the few places in the lower forty-eight states where grizzly habitat still reaches onto the prairie and a wide range of large mammals still lives. Grizzly bears move off the Front and onto the plains. Black bears, mountain lions, elk, deer, pronghorn, wolves, and moose are all present in the landscape. The Front is grizzly habitat in a way that the interior mountain wilderness to the west is not, because the grizzly is a plains animal as much as a mountain animal, and the Front gives them the food resources of both worlds: the root crops and berries of the high slopes and the prairie grass and grain fields below.

The Blackfeet have lived along the Rocky Mountain Front for centuries and call the range east of Glacier their Backbone of the World. The Front as a landscape has been central to their cosmology, their hunting culture, their identity. When you look at those mountains from the plains, you are looking at something that has had a name for a long time.