The sister of my Patrick McGeehan, both originally from Derrylaconnell, Donegal (he who emigrated to Hazelton area and then to Philadelphia) was Mary McGeehan, born around 1865. She married an Andrew McMonigle and they emigrated to Hailey Idaho where they settled and had a number of children and grandchildren. Later to Boise Idaho.
Is it possible you meant Idaho rather than Montana? If so, I have information I can share. firstname.lastname@example.org