The "boom" years of the 1920's were characterized by what?

The "boom" years of the 1920's were characterized by a growth in the use of Automobiles.

While looking at the history of the United States, the 'boom years' of the early 1920s were marked by a huge change in the way people traveled.

Personal transportation was shifting from horse-driven carriages to Automobiles, recently mass-produced by Ford.

At the time, the automobiles were a clear sign of growing economic might of the United States and the optimism of the early 1920s.

The invention of mass producing the automobile in the 1920's was a part of the "boom." Therefore the widespread use of the automobile and an increase in buying is how the 1920's "boom" years were characterized.