Answer:
Railroads
Step-by-step explanation:
Right after the decadesthat followed the Civil War, the United States brilliant emerged as an industrial giant full of energy and space to grow to all directions , specially to the country side. Old industries expanded, changed some business and got many new ones, It refers to petroleum drilling, steel manufacturing, and electrical power, rubber exploration and others emerged. Railroads expanded significantly, bringing even remote parts of the country into a national market economy. With those railroads the country was literally united and walking as a unique body, growing as fast as they could, expending and making the country what it is today.