What was an easier route through the rockies than the one discovered by lewis and clark?

There are several much easier routes through the Rockies than the Lewis and Clark route. South Pass (through Wyoming) was passable for wagons and commercial goods. Marias Pass (the present route of Highway 2) in Montana is much easier and is very close to the Lewis and Clark route, but would have required an overland trek through hostile Blackfeet Indian territory.