1900 to 1929: The spread of the automobile from rare, unimportant toy for the rich into a normal piece of household equipment is perhaps the most significant industrial change from 1900 to 1929. In 1900, cars were assembled one at time by skilled craftsmen. They basically built each car from scratch in one room. The process was slow and very expensive. Only a few thousand cars could be made in a year.
An ambitious engineer and automobile enthusiast named Henry Ford set the land speed record in 1904 by driving such a car at 100 miles per hour.
Ford decided to try to produce cars in stages by moving them along through a factory on a conveyor belt: the assembly line. The cars would have to be simple and easy to put together. They would all have to exactly the same for the assembly line to work. (Ford decreed that the customer could have any color he wanted, as long he wanted black.) The Model T was born.
Cars would have to be produced in huge numbers to justify the expense of setting up such a gigantic factory. No clear market existed for the cars. There were not enough rich people and it was unclear how the working class could afford the car. Ford came at the problem from two directions: wage increases and production efficiencies. Ford doubled wages in his factories, driving up industrial wages everywhere. Now the working class would have the purchasing power to buy Ford's cars. Ford's engineers worked constantly to reduce the cost of making the cars. The price of producing one car went down and down and down. Ford, and his imitators, sold cars by the millions.
In just one generation, the entire population was exposed to cheap mobility. Cars changed everything: people could commute to work in a new way; people could get from the farm to the city easily and quickly; teenagers could escape their parents' gaze; and Sunday afternoon became the time for the family drive; cities dug out from under a veritable mountain of horse dung and carcasses. By 1929, most families in America had their own automobile. The entire population could get into cars and drive away at one time.