All states surrounding North Dakota went to an 80-mph speed limit years ago, and now, North Dakota will become the next US state to allow legal speeds of 80 mph ( into effect August 1st) on stretches of multi-lane highway (up from 75)

The North Dakota Legislature turned to South Dakota its southern neighbor for some real-world statistics. South Dakota raised its speed limit on most limited-access highways to 80 mph in 2015. In the years since, there's been no appreciable change in crashes or fatalities.

Minnesota still remains at 70 mph... and that's not likely to change because of the larger population 

https://www.motor1.com/news/758889/north-dakota-80-mph-speed-limit/