Somewhen around 1900...
You want to convert the country to running that silly carriage thing with a loud stinky engine? You want to ship the fuel from wells all the way from Texas to New York, when we've got fields growing hay right outside the city? Furthermore, where are you going to put all those things? Horses fit conveniently in stalls, and you can put several stalls alongside each other and across from each other in a long hallway. Can you do that with your carriage toy? I don't think so.
Furthermore, what happens when you go to another city? You'll need those fuel dispensing places all over the place to prevent your gizmo from running out of fuel.
Take a look at the whole problem...
OK, so I'm screwing around, but if we've already built several national infrastructures (highway system, power grid, cable TV, gasoline infrastructure, cell phone network, natural gas, etc...) why do people suddenly think it can't be done again? Of course it won't get done over night. None if it ever is. But the country woke up one morning and discovered that everyone was driving cars. Provide a cheaper way to use energy and the profit is built in. You use the proceeds from the profit to build out your infrastructure. You know, like has been done many, many times in the past century.