How did mountains hinder westward travel

Mountains hindered westward travel in many ways.
1) the mountainous paths were dangerous and did not point to a particular direction.
2) one had to pass through several difficulties while passing the mountains.
3) there was increased danger of being lost or being attacked
4) one could not pass mountainous pathways quickly, it sucked up a lot of time
5) Riddled and confusing weather also played part in hindering the westward move  

The mountain paths were dangerous and couldn't guarantee a safe travel- for example, mountain lions are a true fact. Also, the climate and weather conditions in mountains were too risky, so they had to go around them