I too enjoy looking at the construction techniques used. The mortise and tenon joints were cut while on the ground and then assembled in place. My grandpa did a lot of that and those old guys were pretty good with geometry. As a small boy my dad’s job was to make the wooden pegs they used on the mortised joints. They’d take a square piece of wood about 1”x1” and drive a pipe down over them to round the corners.

In Missouri most of those really wide boards were cottonwood or sycamore because both trees would grow really large. Cottonwood is very susceptible to decay but has an outstanding ability to hold paint and retain it for years, thus it was often used for siding.

I once tore down a big old barn and found a number of empty whiskey flasks shoved behind the posts and on top of the beam holding up the loft floor. I’m guessing the missus wasn’t real fond of her husband’s drinking, thus he had to do it in the privacy of the barn.