What made the transition from one-at-a-time manufacturing to mass production possible?

The transition from one-at-a-time manufacturing to mass production, in which large amounts of goods are produced, was made possible by a first step that was the development of interchangeable parts. These similar parts made it possible to put a machine together on the assembly line in little time. Although the use of interchangeable parts was used by some people before him, Henry Ford is usually given the credit for perfecting mass production.

what the first or next guy says

i also think he is correct. i believe they came to washington to protest their rights.