I would venture to say that the mass production of the Model T by Henry Ford was for sure the greatest manufacturing achievement in this country. Henry Ford made the mass production method that is still used today, and the production of cars is one of the top industries across the globe.
It was the production of the Model T that introduced the assembly line, a new and more efficient way of manufacturing products. Before the assembly line, every product was made by one person (usually a specialist), and parts were not interchangeable. By making all parts of a product equally interchangeable and easy to assemble by someone with very little skill, products could be made faster than ever. Were it not for the Model T or the assembly line of production, mass production would not be anywhere near the level it is today.
The production of the Model T was not only a great achievement for America, but for the world as well. This spurred off a lot of technology that we still use and improve upon today and in various different countries. A lot of things would not be possible without the Modle T.
I do believe that Henry Ford's production of the Model T automobile is one of the greatest achievements in American manufacturing in the 20th century. It's very easy to see from highways, byways, and streets that Americans love their vehicles. It's an idea that has spread across the entire world.
Although Ford's Model T was an important invention, it was not the most important one of the 20th century. There were many other important inventions that changed the world just as much, if not more. People's lives changed with the creation of telephones and computers, which not only helped industry but also let us communicate better.