A production line is a set of sequential operations established in a factory whereby materials are put through a refining process to produce an end-product that is suitable for onward consumption; or components are assembled to make a finished article.

Typically, raw materials such as metal ores or agricultural products such as foodstuffs or textile source plants (cotton, flax) require a sequence of treatments to render them useful. For metal, the processes include crushing, smelting and further refining. For plants, the useful material has to be separated from husks or contaminants and then treated for onward sale.

With increasing use of steam power, and increasing use of machinery to supplant the use of people, the integrated use of techniques in production lines spurred the industrial revolutions of Europe and the United States. It wasn't until the implementation and mass production techniques that the US was able to pass the output/capita of the rest of the world. Much of this growth can be similarly attributed to taking advantage of numerous natural resources and raw materials through legislation and laws. And therefore in 1910, the US growth surpassed that of Britain. (Industrial output/worker) Thus, from the processing of raw materials into useful goods, the next step was the concept of the assembly line, as introduced by Eli Whitney. This was taken to the next stage at the Ford Motor Company in 1913, where Henry Ford introduced the innovation of continuously moving the cars being assembled past individual work stations. This introduced the idea of standardisation.