Turning south toward Montana along Hwy 95, there are two fantastic places on your left that I recommend stopping at to check out. The first is Radium Hot Springs, which is just a warm place surrounded by all this cold. After being so cold this whole trip it was great to be outside and not be wearing 4 layers of coats and still freezing. The picture below is of one of the boring pools but they had more interesting pools in the trees behind the building too, it was great.
Second interesting thing was Columbia Lake and the beginnings of the Columbia River. While living in Washington I saw the Columbia River every day out of the windows in my kitchen and living room. So many of the trips I took were along the river, or to dams in the river- it has really been the narrative of my journey in Central Washington. I feel a very strong connection to this river. It felt like a full-circle moment to see the lake where it flows from, and its tiny beginnings of a stream on my last trip in the Northwest.