[chris (OP)]

Jeff Kirtland got in touch with the following observation:

Yellowstone is a continental hotspot, which is fed from near the mantle core boundary.  (The Boise Valley traces the track of the hotspot). Hawaii is an oceanic version.  Both are not related to seductive [sic] activity, like the Cascadia subduction zone. 

Now, will an eruption at one cascade volcano trigger activity at another?  Unlikely.  Ever wonder why the volcanoes are roughly 100 km apart?  This is the “catchment” area for the plumbing beneath each volcano.  Furthermore, if you look at the Cascades, the main chain is inland from the youngest and most active volcano—Mt St Helens. 

The inland volcanoes are largely inactive and are likely to produce lahars and eruptions associated with the mountain collapse, but not full on eruptions (damage could be in the 100s of billions if Mt Rainier failed, however). 

There is the postulate that a new chain may form along the longitude of Mt St Helens, but this is only a postulate.

What does everyone think?

[Bass]

All of the Cascade volcanoes, including the "inland" volcanoes, are considered active with potential to erupt. Check the USGS CVO (Cascades Volcano Observatory) website for more information https://volcanoes.usgs.gov/observatories/cvo/cascade_volcanoes.html
Almost all of the Cascade volcanoes have erupted within the past 4000 years (which is an extremely short geologic time span). There has been very recent activity, including earthquakes and/or ground movements at Ranier, Hood. South Sister, Baker, and Mt. St. Helens.