Yes, buses existed, but the require roads to be useful. The poor road infrastructure in the northern Rockies made long-distance travel by them painfully slow (and probably literally painful). The majority of highways up here were still gravel, very winding, often narrow, rutted, and covered in snow and ice anytime after about mid October over the mountain passes. Bus travel from Seattle to Missoula, if it even existed in the 1920s, would have been anything but "comfortable and inviting" and would have taken forever.
That is probably why in its first 15 years in the PCC, Montana never hosted a true home game against a California team in its own conference. Those road trips would have just been too impractically long to make, some would say "brutal," in the first half of the 20th Century.
. But my research reveals Montana joined in 1924. I also found this:
