7 Answers

 John Kenneth Galbraith stated this in his class at Harvard on the History of Banking and Finance that Adam Smith in “The Wealth of Nations” published in 1776 described in his book the manufacture of pins on an assembly line as a way to increase production of any product in greater numbers by the adaptation of this process. Machines were just coming into vogue at the time and machine development was avant-garde.

Industry.

Two cavemen tired of rubbing sticks to start the BBQ grill.

Population, for one thing. Also the growing middle class, so customers to sell the items to. You need to have a market for whom your trying to sell. Sometimes it's war that increases the great demanding need for certain products as well. There are many factors that caused the industrialization of specifically the U.S., including supply and demand for certain products. New technology is also a contributing factor. Hope this helps although it's rather vague.

Clever people

Technology.