Montanas Crazy Mountains rise between which two rivers?

Yellowstone River is to the south, Musselshell River is to the north. Both of these flow into the Missouri River northeast of the Crazies.

The answer above is describing the Lewis Range and Marias Pass, about 200 miles to the northwest of the Crazies in the Rocky Mountains.

Dude! If you are gonna try to win the Marlboro Challenge you ought to research the answers on the internet or (GASP!) an Atlas. I think it is BS that you are cheating to get the correct answer. I have spent the last 3 hours searching the rest of the internet to get the right answers and then I stumble across this question and I see you trying to perform an end run around the requirements. If you win you might want to reconsider taking the trip because Karma will always bite you in the butt!

The Missouri to the east and the Columbia to the west.

Louis & Clark followed these to get to the Pacific Ocean.