The factory system moved work out of homes and farms. It put work into one building, where workers were paid wages. Young women known as mill girls were the first large workforce in the Lowell cotton mills in Massachusetts. They were mostly 15 to 30 years old. Lowell's first factory opened in 1823. By 1850 more than 10,000 people worked in its mills. It was the top textile manufacturing place in the country.

Many factories in the Industrial Revolution hired children. They could be paid less, and they were small enough to work in tight spaces. Arkwright's Cromford mill hired children as young as seven. Near the end of his time, nearly two-thirds of his 1,150 workers were children. In 1900, about 18 percent of all American workers were under the age of 16. Reformers and new laws slowly ended child labor in factories. In the United States, the Fair Labor Standards Act of 1938 put limits on it.

A second wave of the Industrial Revolution came in the late 1800s and early 1900s. It brought electricity, the production line and a new way to make steel. Mass production became possible once machine tools could make interchangeable parts. Ford used large plants, standardized parts and the moving assembly line. Before the line, his team split one job into steps. Twenty-nine workers each added one part to a magneto on a moving belt.

Quality control means checking products so that bad ones are found before they are sold. At Toyota, a machine or a worker can stop the line when something goes wrong. Just-in-time at Toyota means a car can be built as soon as an order arrives. That works because the minimum number of parts is already stocked along the assembly line.

Words to know

• wages: pay for work
• reformers: change seekers
• quality: how good
• textile: woven cloth