The early United States was overwhelmingly rural. This would quickly change, and New York soon became the center of American commerce. As the cities grew, transportation was an increasingly urgent problem. Some kind of public
transportation would be needed if the cities were to continue developing.

• Mot-clé
  HISTOIRE DES CHEMINS DE FER, EVOLUTION, RESEAU FERROVIAIRE, TRANSPORT URBAIN, TRACTION VAPEUR, TRACTION ANIMALE, TRACTION ELECTRIQUE, ETATS UNIS