This is quite old, but I will still add my limited knowledge for whatever it is worth.
In Midwest USA, Eastern Cottonwood was traditionally the preferred material for barn and hay mow floor boards. This is because of the property mentioned earlier, that it will not be crushed and torn up by heavy machinery but instead mush and then spring back. In this application it is said that cottonwood boards last a very long time. The wood seems to handle stress well. I had once heard, though have been unable to find any evidence to support this claim, that cottonwood was once also used for shakes. This seems doubtful to me, but you never know how much different hand worked word acts!
Cottonwood tends to grow very fast, very tall, and very straight, at least around here it does. It is also considered by most to be a pest. It can quickly spread into drainage channels and clog them up, which is a nuisance for farmers. No one wants to use the lumber from the trees for anything other than pallets these days, so it remains mostly uncut. As a result we have a lot of very old, large cottonwoods around. The old timers used to say that the bigger the cottonwood, the better it was on the saw, They would saw as big of logs as they could handle.