During the Industrial Revolution, American cities were connected by trade largely through the railroads.
In the time before the Industrial Revolution, only a few cities in the US were connected to one another. These were the cities that had water routes between them. In those times, overland transport over long distances was essentially impossible for goods of any real bulk. Roads were bad and loads had to be pulled by animals. With the coming of the railroads, this changed.
The railroads were one of the major drivers of the Industrial Revolution in the US. They allowed tremendous amounts of freight to be hauled over long distances. This meant that cities could be connected to one another and could trade with one another even if they were far apart and even if the goods being traded were bulky. This meant that the country could finally be made into one big market as opposed to several smaller, regional markets.
So, we can say that the Industrial Revolution brought about a situation in which railroads connected American cities to one another and allowed trade to flow between them.
The Industrial Revolution allowed major US cities to be connected for trade by means of the railroad, the intro. of standard measurement and mass production of parts, including standard track size, wheel width,et al.
Next, Trucking Industry, strategic gas stations for refueling, which became full offer truck stops where truckers coul eat, refuel, shower, sleep and renew their long overnight journeys.
Of course, Ship and eventually Plane transportation increased methods of trade.