I'm renovating my house which was built in 1942. Even though these houses were built as temporary worker housing during the war, the 2x4s are just insane quality. Perfectly straight and not a knot to be found in them anywhere. I repurposed some of them as stairway bannisters because they're so great.

Unfortunately, it took me awhile to notice that they're all 3.75" x 1.75". I knew older 2x4s were really 2" x 4" instead of the modern 3.5" x 1.5", but I never knew that there was an intermediate dimensional period like this. I kept building new walls 1/2" too high with them until I figured it out because they looked modern.