Take route wguss recommended. From that direction you'll go through Star Valley, hit Alpine Junction and up through the Snake River canyon. That's 89 to 26. This route avoids Teton Pass which is not recommended for big RVs. Don't know what you are driving or towing, but go around instead through Alpine Junction.
2011 Bighorn 3055RL, 2011 F350 DRW 6.7L 4x4 Diesel Lariat and Hensley TrailerSaver BD3, 1992 Jeep ZJ and 1978 Coleman Concord Pop-Up for remote camping
Dave & Renee plus (Champ, Molly, Paris, Missy, and Maggie in spirit), Mica, Mabel, and Melton