The first time I saw a photo of the Sourdough Ridge Trail it was actually a screensaver for my TV. Needless to say, the views from Sourdough Ridge are some of the best in Mount Rainier & are pretty easy to get to if you don't mind a little bit of quick elevation.
The trail seems like something out of Lord of the Rings with sweeping views practically the entire way not just of the mountain itself but breathtaking alpine scenery.
In the summer this trail is chocked full of Lupine along with a variety of other wildflowers and always provides some of the most epic, panoramic views of Mount Rainier in the park.
These "most luxuriant" of alpine gardens as John Muir described them, explode with color during mid-summer each year. For peak wildflowers, I recommend visiting Mount Rainier's Paradise region in late July and early August.