Question: when did the united states experience its first large industrial expansion

title: Technological and industrial history of the United States
text: In the mid-1780s , Oliver Evans invented an automated flour mill that included a grain elevator and hopper boy . Evans ' design eventually displaced the traditional gristmills . By the turn of the century , Evans also developed one of the first high - pressure steam engines and began establishing a network of machine workshops to manufacture and repair these popular inventions . In 1789 , the widow of Nathanael Greene recruited Eli Whitney to develop a machine to separate the seeds of short fibered cotton from the fibers . The resulting cotton gin could be made with basic carpentry skills but reduced the necessary labor by a factor of 50 and generated huge profits for cotton growers in the South . While Whitney did not realize financial success from his invention , he moved on to manufacturing rifles and other armaments under government contract that could be made with `` expedition , uniformity , and exactness '' -- the foundational ideas for interchangeable parts . However , Whitney 's vision of interchangeable parts would not be achieved for over two decades with firearms and even longer for other devices . 

Answer: answer: In the mid-1780s , Oliver Evans invented an automated flour mill that included a grain elevator and hopper boy, and by the turn of the century , Evans also developed one of the first high - pressure steam engines and began establishing a network of machine workshops to manufacture and repair these popular inventions .