AMP: 257 Location: US-310 and Montana State Line, Big Horn Cty Reassurance shield as we cross into Wyoming. WYO 789 appears out of nowhere and will travel north-south clear to Colorado. At one time it was part of a Multi State Route 789 that went from Canada to Mexico, now it only exists in Wyoming. … Continue reading U.S. Route 310, MT State Line/WYO 789 to WYO 114