My train room sits atop my 36' x 64' 2-story structure. My two 16' RR benchworks are directy over on one of two 12"x12"x66' Doug Fir beams. This whole place was my childhood friend's family owned house and 2-story building. He told me that back in 1960, building the 2-story his dad purchased two beams from a wooden bridge being pulled out due to the forthcoming waters of the new Lake Casitas impoundment. I can not even see a good chance for a purchase today of beams of this size, and to understand that each of these "toothpick" beams could have been cut into 9 of my 12x12 beams! The Pacific Northwest sure had some impressive trees!
I remember around the early 1970s we started to see a drop in lumber quality in Southern California, as lots of 2nd growth Doug Fir was starting to overtake the old growth stuff. The changeover for quite some time is now complete; you can not find old growth, fine grain 2x6 units anywhere, at least new.
Restoring old wooden freight cars today requires some changes, such as glue-lams or even recycled milk bottle constructed beams, as most remaining old growth is too valuable and much goes to window, door and sash mills..