What geographic features of the west might have had an impact on the spread of slavery?

Because of the geography slave owners wouldn't be able to set up their new land without trouble, as the journey through the rocky mountains are dangerous and you would have to be able to get all your slaves and belongings through the mountain range, and the climate in the rocky mountains are not that great for farming as it snows, which would make it harder for their crops to grow.

Explanation:

necessary and proper clause. the congress shall have power to all laws which shall be necessary and proper for carrying into execution the foregoing powers, and all other powers vested by this constitution in the government of the united states, or in any department or officer thereof.