This 400 year old Douglas Fir log rests atop a huge iron base on Railroad Avenue in Snoqualmie, WA. I don't know exactly when they built the shed over the log, but since I've never seen any photos of the log without it, I'll assume that it was erected shortly after they filmed the pilot in 1989. If you look closely you can see the gouges created by the V-shaped, iron support seen in the shot from the credits.
The log's origin is unknown to me. Strangely, over the several years I've gone to see the log in person, I've never actually read the plaque... is there a plaque? Anyway, it's evident that Snoqualmie was a bustling lumber town in the first half of the 20th century, so it's safe to assume that this log is a vestige of its glorious past. Below are some photos from Snoqualmie when the mill was in its heyday --before there were no more giant trees left to chop down!
Here are two vintage photographs of similarly huge fir logs being paraded down the main drag in North Bend, WA. Look, that's the Double R on the right corner!