By the end on WW1, the USA was the richest country in the world. Although it joined the war in 1917, no physical damage was done unlike Europe. Rather its industries were boosted by war production, and through the 1920s the US economy boomed. There were several factors which helped the boom:
- New Industries - electrical goods, automobiles and chemicals. Consumer goods like radios, washing machines, and fridges became widely available
- Mass Production techniques - made goods cheaper so more people could afford them.