Travel infrastructure seems like a 'chicken or egg' problem. Why build a rail line to the middle of nowhere? Conversely how will towns develop if people can't r

Travel infrastructure seems like a 'chicken or egg' problem. Why build a rail line to the middle of nowhere? Conversely how will towns develop if people can't reach them? Much of the development of the heartland US was bootstrapped by the transportation/rail needs between the east and west coasts. I wonder how different the US would be today without the CA gold rush. Or if the gold rush had been somewhere closer to the eastern seaboard like the Appalachians.