191 from Rock Springs Wy to West Yellowstone Mt.

OK, from looking at Streets & Trips, it looks like 191 ends at Daniel Junction where it meets 189. You need to continue northwest (to the right) past Bondurant to get to Hoback Junction. At Hoback Junction 189 goes to the right up to Jackson, while 26 goes to the left (south) to Alpine Junction, which is near the Pallisades Reservoir. A right turn at this junction will take you alongside the reservoir and on to Idaho Falls.