I've hiked there a bit myself!
https://www.flickr.com/photos/miguelvieira/6142136271/
Most of my data came from Eastern Old-Growth Forests by Mary Bird Davis. She defined old growth as forests that were never logged or that are so old that there is no longer any evidence of logging.
The thing with many eastern forests is that because of either their species composition or their site conditions (soil, climate, etc), their trees will never get very large.
What I remember about the Smokies is that no one knew exactly how much they were logged, but the National Park Service estimated about 60 to 70 percent. Most of the remaining unlogged forests won't really have huge trees. In fact, some huge tulip trees that are popular hiking destinations are less than two hundred years old, while small hemlocks on ridges can be over three hundred years old.
I guess I was mostly thinking about the general conception a lot of people tend to have that when they go to something like a national park (particularly in the east), that it's been completely untouched by time, when in fact we had fairly indiscriminate industry and war that giant swathes of places that were only received protections in the early 20th century and beyond.
Oh, and if we're sharing pics of big/interesting trees I would be remiss to skip the road trip where I was fortunate enough to see fat trees[1], dead trees[2], and rare trees[3].
[1] https://www.flickr.com/photos/23215983@N02/26863377690/in/da...
[2] https://www.flickr.com/photos/23215983@N02/26863377830/in/da...
[3] https://www.flickr.com/photos/23215983@N02/27069305001/in/da...