One of the abiding rules in RoadTripping is that there is no single 'best' answer to any question, about route, about sites to see, about how long to drive on a given day, about whether to book ahead or find accommodations as you go, about anything - even what time of day to start. I actually started many of my own RoadTrips at 11:00 pm when I used to work the night shift, because the hours of 0-dark-thirty were my normal awake hours and driving through the first night allowed me to cover ground that I had seen often while there was practically no traffic on the roads.

In you're case, you're leaving from a major metropolitan area and you'd have to traverse Minneapolis, Bloomington, and Shakopee before you hit truly open road. To cover all that ground before the start of a possible rush hour, you'd probably have to leave earlier than 7:00 am. But you have to balance that against the fact that most morning rush hour traffic would be headed in the opposite direction so that your lanes might be relatively traffic free (You know far more about the Twin Cities' traffic than I do), or even the fact that you might be leaving on a weekend (about which I know nothing) when there might not even be a rush hour.

If you're worried about how far down the road you might get before having to stop, that really doesn't depend on when you leave, only on how long you're on the road. No matter how early or late you leave, if you're well rested at the start of your drive, you should expect to cover around 550 miles. Leaving earlier won't help - you'll just hit your physical limits earlier in the day but at the same spot in the road, roughly Kearney NE.

AZBuck