I live in Wis and I can tell you most of the state is very hilly. It doesn't have any mountains, of course, but it has tons and tons of hills.Not as flat as you think
Anytime you have a more than 1% grade, it's a problem.
Union Pacific was the Chicago and NorthWestern, Canadian Pacific took over Soo Lines, that had the Milwaukee track where both of those railroads had fast passenger service between Chicago and Twin Cities, along with the CB&Q(now part of BN-SF), but they followed the Mississippi after Prairie du Chein
SE Minnesota and NE Iowa are similar. There's no new routes to use, you have to pick existing Right of Way