On this day in history...

Except actually, it's "On the day before this day in history", because I had a dentist's appointment and then had to go to work, so I saved a draft "for later."
Anyway.

From Wired, of all places:

April 16, 1813: Specifying the Interchangeability Standard
By Randy Alfred 04.16.08 | 12:00 AM
1813: Gunmaker Simeon North gets a government contract to make 20,000 flintlock pistols, all with interchangeable parts. Mass production takes a massive step forward.

North started as a farmer, but in 1795 got into the business of manufacturing scythes in a mill next to his farm in Berlin, Connecticut. He built a small factory in 1799 to make pistols, and soon landed a government contract for 400 (some sources say 500) pistols. Another contract the following year called for 1,500 guns. Soon, he was operating a pistol factory in nearby Middletown.

From Wikipedia's article on Simeon North:

North is now generally credited with the invention of the milling machine-the first entirely new type of machine invented in America and the machine that, by replacing filing, made interchangeable parts practical. In 1795, North began to produce scythes in a mill adjacent to his farm in Berlin, Conn. Four years later, he obtained a contract to make pistols and began to add a factory to the mill building. By 1813, he signed a contract to produce 20,000 pistols that specified that parts of the lock had to be completely interchangeable between any of the 20,000 locks---the first such contract of which any such evidence exists. The first known milling machine was in use by 1818. At about that time, North was sent to John H. Hall, superintendent at Harpers Ferry (Va.) Armory, to introduce his methods of achieving interchangeability. In 1828, North received a contract to produce 5,000 Hall rifles with parts interchangeable with those produced at Harpers Ferry. North had a 53-year contractual relationship with the War Dept.

Now, I seem to recall that Eli Whitney is often, if not usually, credited with "inventing" interchangeable parts, but Wikipedia's article on Whitney has some revelations:
Interchangeable parts

Though Whitney is popularly credited with the invention of a musket that could be manufactured with interchangeable parts, the idea predated him. The idea is credited to Jean Baptiste Vaquette de Gribeauval, a French artillerist, and credits for finally perfecting the "armory system," or American system of manufacturing, is given to Captain John H. Hall. In From the American System to Mass Production, historian David A. Hounshell described how de Gribeauval's idea propagated from France to the colonies via two routes: from Honoré Blanc through his friend Thomas Jefferson, and via Major Louis de Tousard, another French artillerist who was instrumental in establishing West Point, teaching the young officer corps of the Continental Army, and establishing the armories at Springfield and Harper's Ferry.

By the late 1790s, Whitney was on the verge of bankruptcy and cotton gin litigation had left him deeply in debt. His New Haven cotton gin factory had burned to the ground, and litigation sapped his remaining resources. The French Revolution had ignited new conflicts between England, France, and the United States. The new American government, realizing the need to prepare for war, began to rearm. The War Department issued contracts for the manufacture of 10,000 muskets. Whitney, who had never made a gun in his life, obtained a contract in January, 1798 to deliver ten to fifteen thousand muskets in 1800. He had not mentioned interchangeable parts at that time. Ten months later, Treasury Secretary Wolcott sent him a "foreign pamphlet on arms manufacturing techniques," possibly one of Honoré Blanc's reports, after which Whitney first began to talk about interchangeability. After spending most of 1799-1801 in cotton gin litigation, Whitney began promoting the idea of interchangeable parts, and even arranged a public demonstration of the concept in order to gain time. He did not deliver on the contract until 1809, but then spent the rest of his life publicizing the idea of interchangeability.[5]

Whitney's defenders have claimed that he invented the American system of manufacturing -- the combination of power machinery, interchangeable parts, and division of labor that would underlie the nation's subsequent industrial revolution. While there is persuasive evidence that he failed to achieve interchangeability, his use of power machinery and specialized division of labor are well documented [6]. When the government complained that Whitney's price per musket compared unfavorably with those produced in government armories, Whitney was able to calculate an actual price per musket by including fixed costs such as insurance and machinery, which the government had not included. He thus made early contributions to both the concept of cost accounting, and the concept of the efficiency of private industry.

So why the big deal about Simeon North?

A government contract for 20,000 muskets during what was later referred to as the Second War For Independence! I'm wiling to bet there was a great deal of grousing about interchangeability being a non-essential, if not downright unlikely or impractical, but the War Department got it, and insisted.

Henry Ford is often credited with inventing the assembly line, but between them, North and Whitney set the stage. The Industrial Age was well and truly underway.