I grew up in Bellingham, Whatcom County. Just north of Mt. Vernon, which was mentioned in this thread. Too far to drive to a major city. Don't bother if you want to do stuff in Seattle, to buy anything more than 30 minutes out of Seattle. Going to Vancouver, B.C. is not a viable option because of the variability of the traffic time at the border. Way better to look in King, Pierce or south Snohomish counties. And real estate prices in Bellingham are among the most overpriced in the entire United States (they rank #39 on the top 100 most overpriced real estate markets).
Carnation and Duvall will have land, but it will really cost you because it is in East King County. Everything over there is more expensive than in South King County, a large part of which is "farmland, USA". So is Duvall and Carnation, but it will cost you more to buy there, as I said. Problem is the Microsoft people and others with money drive the price of land up over there. For example, you can't even buy a starter home in Bellevue any more, nor can you in Issaquah. If you push farther north into Snohomish County, you can find less expensive land, such as in Snohomish.
Northbend is farther east, past Snohomish, on I-90, probably another 15 min farther east on the freeway. Yes there are plenty of trees there, but there are in most of these areas if that is what you are looking for. Just remember that trees on your property means crap on your roof and risk of them falling if they are Firs.
However, you may have luck on the East Side with Snoqualamie. But it is out a ways and you can have to deal with more extreme weather out there sometimes. There is land out there. I still think it will cost you more than farther south and west. You also have to go over a bridge to get into Seattle. If there is an accident or Lake Washington is rough and washing over the floating portion, some or all lanes can close.
We live in Auburn. You can find land here. You can also find it in Covington and Maple Valley. We don't have the traffic issues here to get to Seattle, and there are many, many routes to get into Seattle if one is slowed by traffic.
The problem with Black Diamond is that a big bad devloper from the East Side (Kirkland) bought a HUGE parcel of land from King County out there, and will be putting in several thousand homes on it, without buidling infrastructure in the town to handle the traffic. You live out there, you're gonna be in a world of hurt after that project gets completed. It will take you an hour just to get to a major highway on a bad day.
We live in SE Auburn, on land. We have a custom built home and we are 12 minutes from I-5, and 40 minutes from Seattle, to a parking lot or garage in Seattle, on a good day. Sometimes we can get to the James St. Exit in Seattle in 35 min. There are parcels around here that are bigger, and if you go east on SR-18 toward Covington and Hobart, you can find larger parcels if you want them. Longer drive to Seattle, though.
Enumclaw is a good option if you don't mind the extra time to get somewhere. Generally it will take you 25-45 min to get to Auburn, which is farther north and west, then another 30-45 min to Seattle depending on traffic.
I suggest you take your time and look in Auburn, Kent, Maple Valley and even Federal Way (they have land there but you have to look in the unincorporated county areas mainly to find it). Or look in Pierce County, the next county south, in Edgewood or Milton. Relatively close to I-5 and a shorter drive by a longshot than Enumclaw, but not as good as Auburn.
Lastly: if you live in Auburn, Kent, Maple Valley or Federal Way or the areas around these cities, you can get public transportation into Seattle such as the Light Rail or the Sounder Train. The Sounder Train has stations in Auburn and Kent. Light Rail starts in Tukwila but you can drive to it from Auburn, Kent, etc. in a fairly short time or take a bus to there. Cheap, low stress. You can't do that if you live in Bellingham, Mt. Baker, Lynden, Mt. Vernon, Enumclaw, Duvall, Carnation. My wife works in downtown Seattle and takes the Sounder Train every day.