(Still, you gotta admit, it's pretty cool, even if it's the wrong RR ☺)
Check this surprising article from October, 1902. If I were taking the train west right then, I think I'd be a little apprehensive about it. Yes, they could build solid trestles and bridges, but how can you prevent the hillside from moving? According to this page,
"Based on a paper written by Ed Murphy of the ND Geological Survey, the railroad (first Northern Pacific, and now BNSF), have had endless problems with the eastern pier of the High Bridge. Just after completion, the east pier began shifting towards the Missouri River at a rate of 3 to 3-1/2 inches per year. A number of repairs were attempted, but none seemed to work. In 1898, the pier was dug out and moved back onto a larger foundation. By 1902, the pier was already 4 inches off center. After further investigation, it was suspected that the city water reservoir located on a hill above the railroad track was leaking large amounts of water, causing the entire hillside to slide towards the river. The NP built a tunnel under the area to try to drain the water, but the pier continued to move. More projects were completed in 1918, 1923, and 1940 to try to slow down the landslide. In 1951, the NP undertook a major project to cut down the hill and regrade the area. This helped the situation by slowing down the movement to 1/3 of an inch per year, but did not stop the movement". Yikes!