The sod house, or soddy. Not many trees on the prairie, but a very deep layer of earth with lots of grass roots in it. Cut blocks of that, stack them up into walls. They were surprisingly warm in winter,, cool in summer, but also rather damp at times, especially because the roof was a constant problem, and any dirt floor gets really tiresome if you don't want to live dirty. "Miles from the nearest tree" is perhaps a bit much- you could find some trees, but not enough to make into lumber, just enough to turn into poles for roof rafters.

Hey ! I know something! Anyways you dont care.

The point is that while yes sod houses were a big part of the very first settlers here in the treeless plains a very important part of the puzzle is the trains. A lot of the reason early settlements were so limited was because of a lack of building material, but once the railroads got going you could import lumber and export out grain. The rail was a very important part of the settlement of the middle plains in the usa