The original Alaska Lounge in Seattle is located just past security check point 4. It was recently renovated to bring it up to par with the Alaska Lounges at C Gates and N Satellite.
Access to the Alaska Lounge can be purchased by anyone for $60 for one visit or through a yearly membership. Those flying on a paid or award First Class on an Alaska flight that is 2,000 miles or longer can access the lounge. I was able to access it through my travel on a British Airways Club World (Business Class) flight. There are various other ways to get access that you can find outlined here.
You check in on the main level. Immediately to the right is the coffee bar and a small seating area.
On the main floor there is a large seating area.
There is identical for served on both floors of the lounge. During my visit around lunch time there was one hot food item as well as soup and a salad bar.
Up stairs is similar with a seating area and buffet.
Both floors have plenty of natural light and views out towards the runway.
Also on the upper floor is the bar area. It used to be just a window where you could order drinks, but they have expanded it to a true bar with some seating.
Overall the updates make the lounge feel larger with the added coffee area and bar. It is a much needed improvement and brings it up to standard of the other Alaska Lounges.