Building Big
The Outer Limits of Enclosure

5170 Rendering of the Tesla Gigafactory 1, under construction at the Tahoe Reno Industrial Center. Tesla image

IT HAS BEEN SAID THAT Tesla’s Gigafactory 1, currently under construction in Nevada, will be the biggest building in the world, if completed as planned, in 2020. Though superlatives like this are usually more a comparison of ways of measuring than empirical fact, it does provoke a consideration of the outer limits of enclosed space. If the Gigafactory, and the overall economy of scale, suggests that big boxes are getting bigger and bigger (Tesla even has other gigafactories in the works too), then perhaps it is interesting to consider the current state of the art of megaspace.
The Gigafactory is projected to have a footprint of 5,800,000 square feet, inside of which will be two main floors, one at grade and one 41 feet above it. In addition there will be some mezzanines between the two main floors, bringing the square footage inside to somewhere between 12,000,000 and 24,000,000 square feet. The internal square footage projections are dynamic, as the building is being made in more than a dozen discrete blocks, one at a time, adjusting to production methods and demands as they go, and they are currently less than half done. 
But the overall size and shape of the structure, its outer length, width, and height, are likely to remain as projected: 3,600 feet long by 1,600 feet wide, by 71 feet high, or thereabouts. Multiply those three and you get the volume of space that the building encloses, which perhaps is as good a reflection of the total “size” of a building as any: 408,960,000 cubic feet. 
This is still smaller than the current “largest building in the world,”* Boeing’s aircraft assembly building in Everett, Washington, where commercial airliners including the 747 are built, and which encloses 472,370,000 cubic feet. That building, though, is mostly open space, on one level, with a roof that is 19 feet higher then the Gigafactory (90 feet vs. 71 feet). If you took out that extra “headroom,” the Gigafactory would be larger, as its footprint is nearly a million square feet more than Everett’s 4,280,000 square feet. But who’s counting? (Lots of people, actually.)
5171 Boeing’s Everett assembly plant, slightly larger than the Gigafactory by some ways of measuring. CLUI photo

Just Plane Big
It makes sense that the production center for the biggest airplanes is the biggest building, since airplanes are likely the biggest mass-produced objects humans make indoors. 
The Boeing plant, located at the north end of Paine Field in Everett, is much larger than most aircraft manufacturing sheds. It is also exceptional in that it was not built by the US military, like most of the other large aircraft plants in the country. Though Boeing had a presence at Paine Field during the war, the current Everett Plant was built in 1966, to produce the first 747s for the commercial market. The other two primary Boeing production areas in Washington, at Boeing Field, and at Renton, both have sheds containing around a million square feet, not even close to Everett’s 4,280,000 square foot building, which, incidentally, sits next to another building with 1,200,000 square feet and 131,000,000 cubic feet, built to make wings for the 777 aircraft, which is on some lists as one of the ten largest buildings in the world, by volume. 
Like many things in the USA, the largest airplane manufacturing buildings have their origins in World War II and the decade following it, when the Air Force designated dozens of weapons production facilities as strategically essential Air Force Plants. These were generally government-owned, contractor-operated manufacturing centers for planes, rockets, and other strategic materiel, commissioned by the federal government but made by corporations. 
At least a dozen of the 85 official Air Force Plants are aircraft assembly sites, with building footprints in excess of one million square feet. The rest of them are things like aircraft engine plants, and missile plants, which tend to have smaller buildings. Though some have been demolished, many of them remain, in some form. Together they are probably the largest collection of the largest buildings in the country.
Air Force Plant Number 4, for example, is a former bomber plant west of Fort Worth, Texas. It has a building that is nearly a mile long and 650 feet wide, a footprint of more than 3 million square feet. In the 1940s and ‘50s, B-36 bombers were made here by Consolidated Aircraft, later Convair. Now it is operated by Lockheed, and continues to be one of the largest military aircraft plants in the US, making F-16s, F-22s, and F-35 fighter planes. The plant’s various buildings cover more than 6.5 million square feet, and employ around 17,000 people. 
At Air Force Plant Number 6, in Marietta, Georgia, Lockheed made the C-5, the largest transport aircraft currently in use by the US military. The plant was originally a Bell bomber plant in WWII, but has been one of Lockheed’s primary large aircraft assembly plants since 1951. During the Vietnam War, more than 32,000 people worked there, mostly making military transport planes like the C-130, C-141, and later, the C-5. The main assembly building has a footprint of 2 million square feet. 
Air Force Plant Number 13 was a Boeing bomber assembly plant in Wichita, Kansas, built to be further inland and out of range of enemy fire, unlike most of Boeing’s production near the coast in Washington State, and able to deliver its planes quickly to either the Atlantic or the Pacific theater. The Wichita plant made hundreds of B-52s and B-29s, in a building with 2.7 million square feet, next to others that total that amount again. 
Boeing sold it to Spirit Aerosystems in 2005, and though whole bombers are not made there anymore, Spirit still makes aircraft subassemblies for military and civilian aircraft at the plant, for companies that include Boeing.
And Air Force Plant Number 1? That was the Martin plant near Omaha, where the B-29s that would become the famous nuclear bomb-dropping Enola Gay and Bockscar were made. Some of the plant was torn down after the war, but the main assembly building, known as Building D, remains. Though large by most standards, at 1,100 by 700 feet, its footprint is less than 800,000 square feet, smaller than many Walmart distribution centers now (though considerably taller). It is located on the grounds of Offutt Air Force Base, home to the Strategic Air Command (now known as Stratcom), which is building a new headquarters, and has said it will be tearing down Building D at some point soon.
Big planes do not always mean immense buildings. The Spruce Goose was the largest airplane in the world from 1947-1952, when it was surpassed by the B-52. Unlike those mass-production planes, where massive assembly plants were needed so that several planes could be assembled at once (like the B-52, of which 744 were made over the years, mostly in Wichita and Washington state), only one Spruce Goose was made, and the hangar it was made in was a mere 225,000 square feet. Though the plane has moved up to a museum in Oregon, the hangar is still there at Howard Hughes’ old airport in Culver City, California. It was used for years as a movie production center, for big things like the Titanic, and is now owned by Google. 
Once they are built and put into service, commercial airliners and large military planes spend most of their lives outside, even when they are not in use, going indoors only for maintenance. Some maintenance hangars can hold several planes, though even so, most are less than 500,000 square feet. The biggest aircraft hangars, in cubic feet, are those made for airships like dirigibles and blimps. 
5173 Blimp hangar at Tustin, California, one of a dozen or so remaining from the 1930s and 1940s. CLUI photo

Airships were a big deal starting in the early 1900s, when they were used sometimes for transportation, and as aerial surveillance platforms, used especially to spot submarines, all the way through WWII. To keep them out of the wind, and to maintain them, more than 20 large hangars were built at different locations around the United States, mostly by the Navy. 
Fewer than a dozen remain, though they are easy to spot at places like Moffett Field, in Sunnyvale, California; Tillamook, Oregon; Akron, Ohio; and Lakehurst, New Jersey. Most are around a thousand feet long and 300 feet wide, making a footprint of 300,000 square feet, but with a roof more than 200 feet above the ground, they can enclose as much as 50,000,000 cubic feet of uninterrupted space, enough to generate internal weather patterns, some say. Google, always pushing the numerical boundaries, has a 60 year lease on three of them, near their headquarters in Mountain View. 
5174 Airline terminals in China and Dubai are listed among some of the largest buildings in the world, but in the USA, few airport buildings exceed two million square feet. The new Tom Bradley International Terminal at LAX, for example, which cost more than $1 billion, is nearly a half mile long, but less than 150 feet wide. CLUI photo

Big Government Makes Big Buildings
It can take a village to build these megaprojects, and there is no bigger village in the US than all of us—in the form of the federal government. 
During WWII, in addition to aircraft buildings, the federal government was busy making massive and innovative structures for the Manhattan Project, including the gaseous diffusion plant at Oak Ridge, Tennessee, built in 1944 to enrich uranium, which for many years was the largest building in the world. The K-25 building, as it became known, had a footprint of 1,640,000 square feet, and a volume of 97,500,000 cubic feet. It was in use until 1985, and torn down in 2013. 
Two other gaseous diffusion plants were constructed in the 1950s, at Paducah, Kentucky and Piketon, Ohio. While the enclosed space at both of these plants totaled more than 5 million square feet—as much as 10 million square feet at the Ohio plant—it was in separate, though adjacent buildings. Both of these plants are now closed, and undergoing decontamination before eventually being demolished, possibly. Like the big dirigible hangar in Akron, the Ohio plant was operated by Goodyear until it was taken over by Lockheed in 1986.
5175 NASA’s Vehicle Assembly Building at Cape Canaveral, the “tallest single-story building in the nation.” CLUI photo

Rockets can be big things too, though our ICBMs are less than 60 feet tall, making them relatively easy to build and move around. Really big rockets, like the Saturn V, which took men to the moon, were developed at places like NASA’s Marshall Space Center in Alabama, where their engines were tested on outdoor stands. Launching was mostly done at Cape Canaveral, where rockets would arrive in separate pieces from manufacturers, then  be assembled at the launch site. 
This was done in a large vertical building, the Vehicle Assembly Building, which is still there. Since it was vertical, it has a relatively small footprint, 348,000 square feet, but is 526 feet tall, and encloses 130,000,000 cubic feet, making it among the largest buildings in the nation. It is the tallest single-story building in the nation, and the tallest building outside of a metropolitan center. 
The big pieces of these rockets were too large to fit in a plane, train, or truck, so they would come by boat, which meant that they had to be made at facilities with water access. The largest pieces for the Saturn rockets, as well as the external fuel tanks for the Space Shuttle, were made at NASA’s Michoud Assembly Building, east of New Orleans. The building covers 1,870,000 square feet. The site was first developed as an aircraft plant in WWII, then was taken over and expanded by NASA in 1961, as an auxiliary site for the Marshall Space Center in Alabama, to build rockets for the Apollo Program. It is still used to manufacture the stages of large satellite-launching rockets, built by Boeing and others. 
The biggest satellite launching rockets used today, the Atlas V and Delta IV, though nearly as tall as a Saturn V, more than 200 feet, are narrower, and built in stages, and are assembled at the 1.6 million square foot United Launch Alliance plant in Decatur, Alabama. They are too large to travel over highways or fit in planes, like some smaller rocket components can, so a special ship, the 300 foot long Delta Mariner, built for this purpose with a cavernous loading bay, brings them down the Tennessee River from Decatur, ultimately into the Gulf, then to either the west or east coast launch sites at Cape Canaveral or Vandenberg. At these launch sites are large sheds known as horizontal integration facilities. They are located next to launch pads, where the rocket stages are attached before being lifted vertically for launch. These building are generally less than 500,000 square feet in size. 
5176 The other company currently building the biggest rockets is SpaceX, Elon Musk’s company. The rockets are manufactured at the SpaceX headquarters, on the original site for the Northop Aircraft company at Hawthorne Airport, in Los Angeles. The main manufacturing building for SpaceX is a three-story building with a 300,000 square foot footprint. The rocket stages are shipped by long oversized truck loads to launch sites, where final assembly takes place. CLUI photo
Complex Office Complexes
The Pentagon made some of the largest buildings in the country, including itself, the Pentagon. The five-sided structure with a five-acre pentagon-shaped courtyard in the middle was built in WWII. At the time it was made, it was the largest office building in the nation, with somewhere around 6,500,000 square feet on five above-ground floors, and two underground levels. Its outer diameter is 1,414 feet, wider than the Empire State Building is tall. Around 26,000 people work inside. It has six zip codes, and 20 fast food restaurants. Construction was overseen by Colonel Leslie Groves, who, based on his success with building the Pentagon, was selected to run the Manhattan Project, building even bigger buildings for that.
After WWII, the main business of America went back to business, and the private sector started making really big buildings again. Many of these were office buildings in downtowns, going up instead of outwards, like the Pentagon. Skyscrapers clustered especially in Manhattan and Chicago, both of which claim the tallest, if not the largest, downtown buildings in the country. 
One World Trade Center, by some ways of measuring, is the tallest building in the nation—1,776 feet if measured to the tip of its spire, they say (in fact, though, it is even taller than that, 1,792 feet to the top of its spire). But the height of a building should really be measured to its roof, not its spires, in which case the World Trade Center is 1,368 feet tall (exactly the same height as the original 1970 World Trade Center), and is surpassed in height by two other buildings in the USA.  
With a roof at 1,451 feet, the Willis Tower in Chicago, built in 1974 as the Sears Tower, is still the tallest building in the country, followed by the slender residential tower at 432 Park Avenue in New York City (1,396 feet), built a few years ago. The next tallest building in the country is the Empire State Building, still hanging in there, at 1,250 feet. The Trump Tower in Chicago, which often appears as the fourth tallest tower in the USA, listed as 1,389 feet to the top of it’s spire, is actually only 1,171 feet when measured to its roof.
Closed in by city blocks, skyscrapers are relatively narrow, limiting their overall volume. The base of the World Trade Center is only 200 feet on a side, and the nation’s second tallest building, 432 Park Avenue, is only 100 feet on a side. Unlike 432 Park Avenue, most skyscrapers taper as they go up, further shrinking their volume. The Willis Tower, which starts with a base more than 250 feet on its long side, is staggered as it goes up, like cigarettes sticking out of a package, which some say was its design inspiration. Still, the Willis Tower is among the widest of the tallest skyscrapers, with 4,500,000 square feet of usable floorspace, making it among the most voluminous buildings out there (60 million cubic feet or so). Still, it is not that far off from its squat Art Deco neighbor, the 4,000,000 square foot Merchandise Mart, built way back in 1930, when it was the largest building in the world.
5177 The Merchandise Mart in Chicago was the largest building in the world when it was built in 1930, and it still is awfully big. CLUI photo

Though long and low, suburban office parks also have big corporate centers under one roof too. The largest of this type of building could be the 3,000 foot long six-story office building for the United Services Automobile Association (USAA) company in San Antonio, Texas. The company, a direct-marketing insurance and financial services company, serving mostly military personnel and their families, claims that its 4,463,000 square foot headquarters is possibly the largest single-occupancy office building in the country.
5178 Shopping malls are another megastructural form, and there are more than a dozen of them that exceed 2 million square feet. With 2,779,000 square feet, the Mall of America, outside of Minneapolis, is often considered the largest shopping mall in the land, though the largest may actually be the King of Prussia Mall, outside of Philadelphia, bigger by 14,000 square feet, or so. CLUI photo
All Play and No Work
Some of the largest non-industrial buildings are Las Vegas casino resorts like the Palazzo, Las Vegas, with 6,948,980 square feet, in a single structure with a footprint of over 2 million square feet. Elsewhere on the Strip are at least six of the ten largest hotels in the World, topping the list with the Venetian (7,117 rooms), MGM Grand (6,852 rooms), and City Center (6,790 rooms). 
Though massive in scale, these casino resorts may enclose many millions of square feet, but push the definition of what a building is by having multiple structures built at once or at different times. City Center, for example, though conceived as a single development (one of the largest single private developments in US history—built at a cost of more than $9 billion) has 16,797,000 square feet of floorspace, but it is divided into several structures, designed by different architects, even. Is this a single structure with a multiple-building theme? Maybe so. 
Las Vegas is known to house some of the largest trade shows and conventions in the nation, and the Las Vegas Convention Center is indeed one of the largest venues of this type, with more than 2 million square feet of exhibition space. Only a few other convention centers seem to have exhibition floorspace as large or larger than that, including McCormick Place in Chicago, and the Orange County Convention Center in Orlando, Florida.
Though they can have much smaller footprints, enclosed stadiums are much taller than convention centers, and are among the largest buildings out there. Likely the largest of these is the AT&T Stadium in Arlington, Texas, where the Dallas Cowboys play football. It cost more than a billion dollars to build, and can hold more than 100,000 people. Though it has a footprint of less than a million square feet, it contains more than 100 million cubic feet under its retractable roof. This may or may not be the largest enclosed space in a stadium (and thus the largest column-free space in the nation), as other stadiums claim to have a similar volume. The Superdome in New Orleans, with its fixed roof, is said to contain a volume of 125 million cubic feet. Either way, these epic enclosures are still considerably less than the 472 million cubic feet inside Boeing’s aircraft assembly building in Everett, Washington. 
Spanning Space
Steel manufacturing sheds, which can be as much as a mile long, like at Burns Harbor, Indiana, are also among the largest buildings out there, though usually very narrow. Some aluminum plants, too, can be a mile long, like Alcoa’s at Riverdale, Iowa. Hard to say if these are single buildings, though, as they are often made up of a series of long sheds built in stages over the years. There are a few metal shipyard sheds that are large and built all at once, but none larger than one at the Austral Shipyard in Mobile, Alabama, which has a footprint of 734,637 square feet, and a ceiling height of more than 65 feet, making for a volume of 48,204,000 cubic feet.
Buckydomes and Biospheres may seem like big structures, but they actually aren’t, in the big picture. Biosphere 2, in Oracle, Arizona, encloses around 7,200,000 cubic feet under glass, on a footprint of 3.14 acres, which is less than 137,000 square feet. The largest geodesic enclosure in the USA is likely the Spaceship Earth sphere at Epcot, in Florida, which opened in 1982. It has a diameter of 165 feet, enclosing a volume of 2,352,000 cubic feet. A larger geodesic sphere was built for Expo 67, in Montreal, with a diameter of 250 feet. Now called the Biosphere, it is not quite a complete sphere, and contains around 7 million cubic feet, similar to the Biosphere 2. 
Other monolithic dome structures, geodesic or not, span large-ish spaces, like the Climatron at the Botanical Gardens in St. Louis, or the aviary at the Queens Zoo, a low dome with a 175-foot diameter that was originally built for the 1964 World’s Fair. Bigger domes have been used to enclose spaces for things like university sports arenas, but even the largest of these, like the Superior Dome at Northern Michigan University, in Marquette, Michigan, is only 535 feet in diameter, enclosing a space of 222,150 square feet. An impressive-looking megastructure, even more so as it’s made of wood and not steel, but still smaller than some Walmarts. 
Speaking of Walmarts, the company is, unsurprisingly, likely the largest container of space in the nation. With around 3,500 supercenter stores in the US averaging 179,000 square feet each, that’s 626,500,000 square feet, or more than 22 square miles. That doesn’t include Sam’s Clubs or other types of stores the company operates. In addition, there are more than 100 distribution centers for the company across the country, whose sizes range from 500,000 square feet to more than a million square feet. 
Where House the Warehouse
Regional storage and distribution centers are one of the fastest growing types of buildings out there, and hundreds of them, possibly into the thousands by now, surpass a million square feet (the equivalent of 500 feet wide and 2,000 feet long). Company-dedicated warehouses at ports and production nodes are especially large. For example, an import warehouse for Target at the port of Savannah, Georgia opened in 2007, and has more than 2 million square feet. Another on the west coast, at Lacey, Washington, is 1,700,000 square feet. John Deere’s Parts Distribution Center in Milan, Illinois, just a few miles from its company headquarters in Moline, is located next to the airport and is 2,800,000 square feet. Michelin Tires recently built a distribution warehouse near its factory in Spartanburg, South Carolina, which is said to be 4 million square feet. 
In some cases internal logistics hubs have formed near UPS and FedEx nodes. Nike’s 2,800,000 North America Logistics Campus, opened outside of Memphis, has a BNSF intermodal yard nearby, next to FedEx’s national distribution hub at the airport southeast of town. These remote warehouse nodes can emerge in the middle of nowhere, where real estate is cheap, at the sweetspot between major cities and ports. Like at Grapevine, California, population zero, where Ikea built its largest distribution center in the US, a 1,725,000 square foot warehouse, because it was on the interstate halfway between the Bay Area’s urban sprawl and Southern California’s urban sprawl. Also, importantly, it was between the port of Los Angeles and the Port of Oakland, so the company could shift its deliveries between the two, as needed, as both were a few hours away either way, a day’s round trip for a trucker. 
This kind of mega-region logistics is what has created the Tahoe Reno Industrial Center, a rapidly growing logistics center outside of Reno, Nevada, four hours from the Bay Area, but beyond the expensive real estate and regulatory environment of California, and where the Gigafactory, possibly the second largest building in the country, is currently under construction.
The Gigafactory is a battery plant, but is also a car factory, manufacturing parts for electric cars. Given the scale of the car industry, 265 million registered cars on the road, and up to 20 million new ones being sold every year, it is not surprising that the structures for the automobile industry in the USA cover more ground than nearly any other. 
Some of the largest corporate buildings are car company head-quarters, like GM’s Renaissance Center in Detroit, which has 5,540,000 square feet, and  Chrysler Headquarters and Technology Center, in Auburn Hills, Michigan, which has 5,300,000 square feet and a contiguous office complex with a central building that is half a mile long. Ford’s headquarters in Dearborn is more modest, but is close to the company’s famous River Rouge Plant, one of the biggest industrial sites in the country today, as it was in the 1920s, when it was cranking out Model T’s, the first car for the masses.
“The Rouge” had more than a square mile of vertically integrated production, going from piles of raw material coming in by boat for making steel, to finished cars, spread over 93 buildings, and nearly 16 million square feet of factory floor. Though the parts for Model T’s were produced at Rouge, the final assembly actually took place at the Highland Park assembly plant. Over the 19-year span of production, more than 16 million Model T’s were produced. In 1927 the Model T was finally replaced by the Model A, which were produced at the Rouge plant from 1927 to 1931. Almost 5 million Model A’s were made, but by then it was just one among many cars being produced by American manufacturers. Though the connected steel sheds at the center of the Rouge site cover more than 3.3 million square feet, there is no single megastructure at Rouge. It continues to be an active industrial site, with a steel plant owned by another company now, a manufacturing plant for Ford cars, and a modern plant with around 2 million square feet, which assembles the F-150 pickup. Made since 1948, the F-150 has been the best-selling car in the USA for more than 35 years.
The Highland Park plant, north of downtown Detroit, was where Ford’s assembly line method changed the world of mass production. When it opened in 1910 to assemble the Model T, it had 90 acres under one roof, nearly 4 million square feet, the largest manufacturing plant in the country. When the moving assembly line was implemented there in 1913, manufacturing time for the Model T went from 728 minutes per car to 93 minutes, making the car affordable and available to many more people. The plant could produce a million cars a year. After production for the Model A went to the River Rouge plant, the Highland Park plant made parts, Sherman tanks in WWII, then eventually became storage, with buildings leased to other companies. Today, just a few pieces of the original complex remain, vacant or used for warehousing, and the rest are open lots, parkland, and a shopping center.
The moving assembly line vehicle manufacturing developed at Highland Park has been recreated all over, starting at Ford Model T plants at other cities too, like Chicago, then spreading out all over the world. Today there are around 40 active consumer vehicle assembly plants in the USA. General Motors, for many years the largest company in the nation, has a dozen large vehicle assembly plants in the USA, in Texas, Kentucky, Kansas, Tennessee, Missouri, Ohio, Indiana, and five in Michigan. In addition, the company has numerous parts plants, making engines, transmissions, and other components. GM still sells more cars in the US than anyone, around three million per year.  Most of its assembly plants are between two  and four million square feet.
Ford, which sells around 2.6 million cars a year in the USA, has eight assembly plants at the moment, which generally range from three to 4.7 million square feet. Chrysler, (now Fiat/Chrysler), sells around 2.2 million cars per year and has five assembly plants in the USA, ranging from two to five million square feet. Toyota, which sells around 2.4 million cars in the USA, has five plants in the USA too, including a plant in Georgetown, Kentucky, which makes more than 500,000 vehicles a year, and has 7.5 million square feet, likely the largest car plant in the country. Nissan’s plant in Smyrna, Tennessee, one of two the company has in the USA, has 5.9 million square feet, and is likely the second largest car plant in the country. 
Not too far down the list of “largest automotive assembly plants in the USA” is Tesla’s current vehicle assembly plant in Fremont, California. It was built in 1962 by General Motors, and grew over time. Starting in 1984 it was operated as the New United Motor Manufacturing Plant, a partnership between Toyota and General Motors, making things like Toyota Corollas, until 2009, when it was the last car assembly plant in California to close. In 2010, Tesla bought it, reversing the trend, though it took a while for it to grow into the space, which is usually listed as somewhere between 4,300,000 and 5,500,000 square feet. Like many megastructures, the interconnected factory complex is not all enclosed in one building, but at a half mile long by a third of a mile wide, it’s pretty damn big, no matter how it measures up. ♦
5183 Tesla, Fremont, CA. Tesla’s only vehicle assembly plant covers around 5 million square feet. CLUI photo