Some areas of Montana don't even have a speed limit any more. And apparently they've got less accidents than areas with speed limits.Varies wildly in my experience. 14 years ago, drove through Montana, Wyoming, South Dakota, Iowa, Illinois (went to Chicago), and back through Wisconsin, Minnesota, and North Dakota. I'm not sure how many of those actually had the same limits on the interstates. IIRC, SD had the highest limit. 80-85Mph IIRC. With good reason, great straight roads!