The last major eruptive period for Mount Rainier was around 1,000 years ago, but even in that incident, there were no lava flows. More recently, in 1894-95, there were small summit explosions reported by observers in Seattle and Tacoma. It is important to note that while Mount Rainier has not had a magmatic eruption in over a millennium, it is still considered an active volcano, and scientists continue to monitor it for any signs of reawakening.
Holyscroller was a Freeper, and she wrote 4 books on Mt Rainier. (She passed in 2020). Whereas they say Mt Rainier had no “lava flows” they are correct, but Mt Rainier has had a lot of pyroclastic flows, which could be more dangerous than lava. A pyroclastic flow is when superheated steam interacts with dirt to create boiling mud. Evidence suggests that multiple times Rainier has sent this boiling mud down, with walls of it up to 60 feet deep, traveling at 60 mph, and making it as far as Puget Sound at Tacoma. Pyroclastic mud is more dangerous than lava, because it reaches speeds that lava cannot even begin to approach, and flows much further than lava can (evidence of up to 60 miles).