Yes, Western Hemlock is a different species from what you guys see back East, but the wood is almost indistinguishable.
Rot resistant compared to what though? If I were to compare it to Birch, Hemlock would be excellent. However compared to Cedar, Douglas Fir, and for that matter even Lodgepole Pine, it doesn't hold up nearly so well if it is sitting in a moist environment. I agree that it makes a superb interior structural wood due to its hardness and strength, and is also very good for other uses if properly treated and sealed with paint or stain. But if I were to drop Hemlock, Doug Fir, Lodgepole, and Cedar trees side by side in the bush and left them to rot, the Hemlock would be rotten beyond usability within just a few years, while the Cedar would still be there three or four generations from now and still probably millable. I've even cut into Douglas Fir logs I've found laying in the bush that were left there back in the '40s-'50s when the area was first logged, and while the outer few inches are usually rotten, the inside is still as sound as the day it fell. I'm not saying Hemlock is a bad wood - I love the stuff - I was just stating that it isn't ideal for unprotected use in moist environments.
