Some of the Steam Locomotives pulling passengers could go fast.
From a Tulsa World link that requires a subscription:
Once-sidetracked steam locomotive is taking its place in Tulsa's history
The Frisco 4500, said to once travel as fast as 100 mph, originally steamed through Tulsa pulling the "Meteor" passenger train between Oklahoma City and St. Louis, Yowell said. It was one of ...
The Northerns
The Northern class steam locomotives, with a wheel arrangement of 4-8-4, were used by most large U.S. railroads in dual passenger and freight service. Union Pacific operated 45 Northerns, built in three classes, which were delivered between 1937 and 1944. Initially the speedy locomotives, capable of exceeding 100 miles per hour, were assigned to passenger trains, including the famous Overland Limited, Portland Rose and Pacific Limited. In their later years, as diesels were assigned to the passenger trains, the Northerns were reassigned to freight service. They operated over most of UP's system.
https://www.up.com/heritage/steam/844/index.htmI have flown over a good portion of the rail between Tulsa and OKC. Looks a bit to curvy and through the middle of too many towns for true high speed trains. I think most of the curves would be OK at 80 mph but it might make passengers a bit uncomfortable. It would be nice to see a timetable from when the SF Meteor 4500 was pulling passengers.