From the archives: This story originally appeared in the November 1943 issue of Popular Mechanics. We’re republishing it now as part of our ongoing look back at Pop Mech’s best feature stories from the last 125 years. It appears here as originally published; some details, terminology, or understandings may have changed over time.

Move over Willow Run, Pentagon Building, Merchandise Mart, and Boulder Dam. Make way for Uncle Sam’s giant war baby and Hitler’s latest headache—the Dodge Chicago Plant, Division of Chrysler Corporation. It’s the world’s largest airplane engine factory, and about to move along its assembly lines are some of the world’s most powerful bomber motors.

One building in the immense plant covers some 80 acres of ground, or about 50 city blocks. Nothing like it has ever been constructed. Experienced automotive and aeronautical executives, who are used to doing big things in a big way, are literally flabbergasted by its size, by the thousands of shining machine tools arrayed under a concrete roof that seems as big as the sky.

The only way you can see clearly from one end of the main building to the other is with a pair of binoculars. This mammoth one-story structure, the queen of nearly a score of buildings sprawled over 500 acres, could swallow the Ford Willow Run bomber plant and leave room for 20 baseball diamonds around the edge. It has more floor space than either the War Department’s Pentagon Building or Chicago’s Merchandise Mart. And when the plant reaches maximum production its weekly output of engines will be tremendous.

The great bombers for which these engines are designed are the No. 1 U.S. military secret. But anyone can guess that they are the ships to which Gen. Henry H. Arnold referred when he spoke of the Flying Fortress as “the last of the small bombers.” And anyone can guess that the new Wright engine made in the Dodge Chicago Plant—it has 18 cylinders and considerably more than 2,000 horsepower—will enable bombers to carry record loads of blockbusters on round trips from American bases to Berlin and Tokyo.

That is why the plant producing these engines is regarded as the most important war industry in America today. It also explains why much of the activity in the plant, which is financed by the Defense Plant Corporation and operated by the Chrysler Corporation, is shrouded in secrecy.

At one time there were more than 16,000 workmen and some 1,400 engineers on the job.

A new and speedy type of construction was used for the buildings, which are of reinforced concrete with a roofing of concrete slabs. Even the building arches are concrete. Sixty portable concrete forms, resembling Helen of Troy’s wooden horse, were used to pour the main building. They moved on wheels as the concrete work progressed along the length of the huge structure. The concrete was hoisted up towers and transported in “buggies.” The amount of lumber in the forms would have built 2,000 four-room bungalows.

“With this method of construction, we didn’t have to stop after covering 80 acres,” one engineer said. “We could have kept right on going across the country.”

After the concrete was poured in one section, vacuum pumps sucked water from the cement so that in three to seven minutes the concrete would support the weight of a man. When the section was set, the form was whisked away to a new position in just eight minutes. The amount of concrete used in the construction would make a solid block 100 feet square and taller than the Empire State Building.

Many areas in the plant are blocked off with letters a foot high: RESTRICTED.

But it can be told that this vast plant, enclosed by four miles of fence, will take in raw bars of steel, pigs of aluminum and magnesium at one end and turn out finished motors at the other. It is the only airplane engine plant in the world that will do this. When the engines take their final leave of the testing cells they will be ready for flight.

In construction alone, so many records were broken that Chrysler engineers long ago gave up keeping tab on them. The first ground was broken June 4, 1942. In 12 months all the buildings were completed, and in 14 months many were already in production. During the height of day-and-night construction activity, 150 carloads of sand, cement and stone were brought into the plant every day. In addition, 800 truckloads of building material were used daily.

This type of construction required only one-half the normal amount of reinforcing steel, saving enough of that precious metal to build 14 destroyers and about 600 M-4 tanks.

The principal units of the plant consist of the main building where the engines are machined and assembled; two large foundries, one for aluminum, the other magnesium; light and heavy forge shops; heat-treating and die shop; testing buildings; tool shop; and an H-shaped, brick-faced administration building—the only two-story structure at the plant.

Parking lots accommodate more than 13,000 automobiles. The largest is a block wide and a mile long and situated in such a way as to expedite entrance or exit of thousands of employees at one time. Subways beneath the building speed pedestrian traffic. One busy subway intersection is called “42nd and Broadway.” Openings of the subway are neat washrooms, miles of locker space, and nine model cafeterias that will seat 5,000 workers at one time. There are a total of 14 cafeterias in the plant.

Two immense water towers, made of concrete with cypress tanks to save steel, provide facilities for water lines, while a reservoir holds nearly 3,000,000 gallons. The plant affords enough sewerage, gas and electrical service for a city of 70,000. There are 50 miles of water and gas mains, 500 miles of telephone wire.

Compared with this impressive plant, the engine it produces seems unbelievably simple and insignificant at first glance. It is only when one follows the intricate steps in the creation of this modern miracle that one appreciates its production problems.

At one end of the plant is the forge shop for the heavy parts that go into the engine. Here red-hot blocks of steel are beaten and squeezed into shape by giant hammers. The concrete bases that support the blocks under the hammers have piles that go down to bedrock. The dies that shape the thousands of parts are made in the die shop, and the hard steel tools for cutting the dies are made in a nearby tool shop.

In twin units, each of which would be considered a major industry in its own right in normal times, castings of aluminum and magnesium are made. The world’s largest magnesium castings are poured in the magnesium foundry. If one of these big castings were made of steel, it would be more than a man could budge; as it is, it can be lifted with one hand.

The process of pouring magnesium is one of industry’s most colorful operations. The white-hot metal that has a tendency to burst into a pyrotechnical display unless carefully treated is poured into molds made of sand baked as hard as stone. The molds, of course, are also made in the foundry. Before pouring the magnesium, carbon dioxide gas is pumped into the recesses of the mold to remove all air, for the hot magnesium burns on contact with oxygen.

When the large and small castings are broken out of their molds, rough spots are machined away and they are sent along on the network of assembly lines that feed into the main machining and assembly building.

Here the parts that pour from the foundries and forge shops in a never-ending stream are cut down, ground and polished on the greatest array of lathes, drills and other finishing machines ever assembled. Metal is ground to specifications measured in hundred-thousandths of an inch.

In this building many of the parts receive a final heat treatment to harden their mirrorlike surfaces. Others are painted and treated with chemicals, and some are even plated with tin, nickel or chrome.

Visitors are taken through the building on a platform trailer pulled by a tiny tractor. Beside each seat is a loudspeaker that carries the voice of a company man who sits beside the driver with microphone in hand.

Two-thirds of the main building is used for machining, and a “small” area of about 22 acres is occupied by the sub-assembly, first-run, and final assembly lines. On the sub-assembly line, the finished parts are gathered and put into a specific piece such as the supercharger, pistons or ignition system.

At the end of the first-run line, the engine is lifted from the assembly dolly and placed on a test mount designed to speed the transfer to a test cell, and the job that once took hours is accomplished in a few minutes. In the cell, a generator instead of a propeller is attached to the shaft and the energy is used to make electricity.

After the first test, the engine is completely taken apart and each part is minutely examined. If any defects show up, new parts are substituted before the second assembly begins on the final line.

Workmen have nicknamed the plant “Hitler’s Headache.” One of these days the engines they are building will be roaring over Berchtesgaden.