And then there's the Convair B-36 Peacemaker, with 230ft (~70m) wingspan. The last major piston-engind heavy bomber, design was started in 1941, put in service in 1949, and retired in 1959.

https://en.wikipedia.org/wiki/Convair_B-36_Peacemaker

The plane's also notable for having been one of very few operational flying aircraft carrier types - able to carry https://en.wikipedia.org/wiki/McDonnell_XF-85_Goblin

True.

It was a big bird for its time. It is a shame that none were preserved, though that isn't much of a surprise because even just one of them would be expensive to store and maintain in a non-flyable state.

There is a full size mockup though: https://en.wikipedia.org/wiki/Boeing_314_Clipper#Surviving_a...

"full size" doesn't include the wings, sadly - just the interior and main hull.

I had the general impression B-52s were some of the largest airplanes as well, but when I looked up the stats on Wikipedia it turned out they are quite a bit smaller than large passenger/cargo jets today.

Might be a missing qualifier. For sea planes, that appears to still be an impressive span.