The route we like is to drive up I15 to route 89 near Brigham City. We stay on 89 and 189 all the way up to Jackson. Route 89 between Logan and Garden City is the
Logan Canyon Scenic Byway, which is a beautiful drive. There is about 2 miles of 6-7% downgrade going in to Garden City. We have used this route twice in our Class C and wouldn't hesitate to do so again.
An alternate route is to stay on I15 to Idaho Falls then take route 26 to Alpine Junction, then route 189 up to Jackson.
Whatever you do, don't use route 22 over the Teton Pass between Victor ID and Jackson. Steep grades and sharp curves. Been there, done that, never again!
Just before getting into Jackson from the south on the left is a Smith's supermarket with a gas station, which usually has the best gas prices in town. About 1/2 mile further is an Albertson's supermarket. Stock up at either of these to save $$ and have a better selection of groceries before heading up to Grand Teton and Yellowstone.
