Welcome to THE MAKING OF A NATION -- American history in VOA Special English.In the years after World War One, new technologies changed America. Technology made it possible for millions of people to improve their lives. It also brought great changes in American society.This week in our series, Harry Monroe and Kay Gallant tell more about the technological and social changes that took place in the United States in the early nineteen twenties.Some of the most important changes came as a result of the automobile and the radio.Automobiles began to be mass-produced. They were low enough in cost so many Americans could buy them. Gasoline was low in cost, too.Together, these developments put America on the move as never before.