What had made the economic boom of the 1920s possible?

"The United States of America during the 1920’s, this period was full of excitement and money for the American people. “Boom” is a word used to describe how America expanded economically, as more people were making earning more money, more businesses were opening and America experienced the feel good factor. Additionally the word “Boom” can also be used to show the status of the countries success. The Boom was a period when industry expanded and grew rapidly, transport industry also expanded as roads and cars were built. There were many factors that helped contribute to the Boom, individually and together. " -tahira s from yahoo
https://answers.yahoo.com/activity/questions?show=ENW3BH7DOTWNGXDLV6ZY4VAM4I&t=g

Ifeel like this is a very good quesyion

Italy france germany