The pacific northwest seemed isolated until it became connected with the rest of the us by the creation of

The correct answer should be the transcontinental railroad.

It was a railroad designed to go from one part of the country to another and this was almost impossible before because the journey was long and tiring and wen trough many dangerous areas so people usually didn't want to go that far. The railroad made it possible to get there quickly and safely and this led to the development of the region