Like North Dakota, Eastern Montana highways follow paths of least resistance--the smoothest track. We've had a lot of rain this year, the grass is green six weeks after it usually turns borwn.
There are vast areas of North Dakota and Montana north of the interstate which are too rocky (glacial moraine) or too steep (badlands topography), or are otherwise unsuitable for farming wheat, but make good grazing land.
Vast BLM owned tracts are grazed as well, but farming is out.
If the land will make a good living for those farming it, it is generally being farmed unless the government has put the skids to that.
Corn, BTW, is a relatively uncommon crop here. Between wind loads and water requirements, it doesn't generally do well outside the river bottoms.
My mother-in-law lives in Havre and it is usually brown by July, but not this year. She voted for Obama and claims it is Global Warming that has brought the “monsoons.”