During my tenure as a volunteer firefighter I got to see a lot of buildings that had been built with, shall we say, other than standard construction practices.
In some areas at pioneer times trees were cheap, and milling costs were expensive (often this would be hand sawn) and odd large sized timbers would be used. The first priority was to clear timber so food crops could be grown. It was not until after a food supply was established that enough commercial/industrial activity occurred to allow logging for lumber to become profitable.
Often salvage lumber would be used (usually for outbuildings), again what ever size was big enough and nothing was too big.
I have also seen a house where one of the main sills was the base of a 60" douglas fir dropped into place on boulders... then the house was built using the rest of the wood that was hand milled on site.
Another later unique construction was done by a gentleman who was a laborer at a local lumber mill. They allowed the employees to take the end cuts of boards for personal use. He constructed a house by using 2x4's laid flat and lapped like you would use brick.