Glad to be of help Opus118 and Michal,
It helps knowing about what the land and people are like. Reading the story of the parish in Bonners Ferry it didn't surprise me at all to read that there were people coming from Canada and other traveling hours. That's normal for out home at least for the parts nearer to the border.
At to Montana, as I wrote mining brought Serbians to Butte in the last 19th/early 20th Century and there is a quite established EO parish there that is about 108 years old. The other counties in Montana are another story and I can tell you each one.
They're the counties with the largest cities: Billings, Great Falls, Missoula and Bozeman and the capital of Helana and people end up there for different reasons. Missoula and Bozeman are the big university towns (therefore more in-comers, visitors, students etc). Great Falls has a good sized Air Force base (that's how my family got out there) along with other things. The last I knew though, the Greek parish there hasn't had a priest in many years. They import one 3-4 times a year. Missoula also doesn't have a resident priest as far as I know. Billings is the largest city and it has a parish with an "attached" priest according to their web site.
The missions in Helena and Bozeman don't have a full time priest but have liturgy more regularly than Great Falls. It might be in the old West tradition of the "circuit-riding" priest/pastor/preacher.
So in the fourth largest state there are two parishes (as far as I know) with weekly services and that even with the missions there are people who are hundreds of miles and sometimes difficult drives from any form of EO presence. Montana is about 250 south to north at its widest and more than 600 miles (1,000 Km +) from east to west) fyi.
I hope that is helpful, too.