The Big Boy locomotives are connected to the earth's plate tectonics.

I saw an interview with the captain of the Steam Team, and he said the Big Boys were developed to take freight across the 48 states during World War II, and the biggest challenge was getting from Green River, Wyoming to Ogden, Utah. That land is the Wasatch Range east of Salt Lake City.

I remembered a phrase 'The Wasatch Line' from geology classes years ago, a time when plate tectonics was new and slightly suspect. I didn't understand the Wasatch Line, and I don't think my professor did either. Or maybe, being an oilman, he didn't want to think about it. But yesterday I read an old scientific paper about the Wasatch Line, [WAW-satch] and it's clear that it marks a time long ago when land from northern Mexico into southern Canada ended in a broad curve which goes through Salt Lake City. West of that are thick offshore sediments which piled up quietly, minding their own business for millions of years. To geologists, North America ends about 2/3 of the way [if you're going west] between the east coast and the west coast.

Details after that a vague in my mind. Sea-floor spreading rammed some body or other from elsewhere into those sediments, crumpling them and thrusting them eastward. Seafloor was pushed down (subducted) and melted at depth, mixing with sediments and producing granite. This granite intruded, rose, and pushed up mountains, mountains which got in the way of freight trains eons later. And that's how the Big Boy locomotives were born.

I'm still looking for an explanation of the Uintah [you- INN-tuh] Mountains adjacent to the Wasatch Mountains. The Uintah's run east and west. I believe they are the only mountains in America that do so. In any case, that's rare.