Because they were surveyed first, railroads lie in the best graded route. This matters less in the flat midwest or southeast. In the mountainous west, it matters a lot...in winter you can drive over the Sierras at Tehechapi or Donner, but not in between...well maybe Kern but you aren't gaining anything versus Tehchapi.
Also railroads run to where people want to go: the old towns that were there when they were built and the new towns that sprung up along them.
Further East in Arizona, there's the small matter of the Grand Canyon. You can go south of it year round as I40 (and old RTE 66) and I10 and US80 do. North of it, you'll be closed for snow often. I40 only closes for snow sometimes.
[In the US].
Because they were surveyed first, railroads lie in the best graded route. This matters less in the flat midwest or southeast. In the mountainous west, it matters a lot...in winter you can drive over the Sierras at Tehechapi or Donner, but not in between...well maybe Kern but you aren't gaining anything versus Tehchapi.
Also railroads run to where people want to go: the old towns that were there when they were built and the new towns that sprung up along them.
Further East in Arizona, there's the small matter of the Grand Canyon. You can go south of it year round as I40 (and old RTE 66) and I10 and US80 do. North of it, you'll be closed for snow often. I40 only closes for snow sometimes.