When it opened in 1922, Detroit’s new nine-story police headquarters, designed by Albert Kahn, boasted reinforced concrete construction and the latest high-tech amenity for municipal workers: air conditioning.

Alas, the building’s early cooling system was no match for the deadly heat wave that roared through the Midwest US in July 1936, setting a string of records that still stand.

During that long stretch of 100-plus-degree highs, which claimed more than 300 deaths in Detroit, police officers and staffers in the Renaissance Revival structure suffered along with everyone else (especially after the building’s top-floor radiators were accidentally turned on). “The only result ever attained by putting on the cooling system has been to blow soot out of the apertures and onto the faces of everyone in the building,” the Detroit News reported.

Office work in the US today is deeply intertwined with the all-American invention of artificially cooled air. Regardless of region or climate, the vast majority of indoor workplaces are built around air conditioning, and it’s been that way for decades. (As of 2020, about 90% of US homes have access to some kind of AC, too, but that still varies considerably by geography, and the share has shot up dramatically since the 1970s.) From Maine to Florida, the expectation that white-collar labor is to be performed cocooned in a climate-controlled atmosphere is so firmly established that it can be hard to imagine — especially during the anthropocene’s ever-more-torrid summers — that American office workers once sweated through a very different kind of workday.

Picturing a desk job of the pre-AC era might bring to mind a noirish scene from an old detective movie — a desk fan stirs the air and shafts of unforgiving sun blaze through window blinds as the gumshoe mops his brow and perspires through his suit. That’s basically what you’d find in offices in downtown New Orleans in the early 20th century, says Tulane University geographer Richard Campanella.

Electric appliances like table and ceiling fans became workplace staples in the 1910s, and commercial buildings were designed for maximum ventilation, with high ceilings, transoms and tall windows shaded by awnings or shutters.

For men at work, business attire was a light-colored suit — the cotton seersucker suit was popularized, if not invented, by New Orleans clothier Joseph Haspel in 1909. But by far the most important means of coping with excessive heat was psychological; in warm-weather cities, an elaborate set of social practices evolved to support living and working in high temperatures.

“Like people throughout the subtropic and tropical regions, New Orleanians historically expected summertime to be hot and humid, indoors and outdoors,” Campanella says in an email. “It was a condition that one expected, and to which one adapted; it was not viewed as a problem to be solved.”

Air conditioning changed that — but not right away. The earliest systems of the 1900s were installed in theaters, factories and textile mills, where temperature and humidity control were desperately needed. Curiously, desk workers in the urban south didn’t get AC much more quickly than those in more temperate northern cities. Among the earliest non-industrial buildings to be fitted with a cooling system, in 1902, was the trading room of the New York Stock Exchange.

In 1928, air conditioning pioneer Willis Carrier figured out how to get chilled air into into a skyscraper when the 21-story Milam Building in San Antonio opened with a built-in Carrier “Manufactured Weather” system. But while department stores and banks were often mechanically cooled by the 1920s, relatively few prewar employers saw the value of what was then called comfort cooling, which was seen as a luxury amenity unfit for the office; 1930s New York City office towers like the Chrysler Building and the Empire State Building opened without central air.

Under such conditions, indoor workers were routinely just sent home in hot spells. Employers relied on a formula to determine when conditions were too oppressive, historian Gail Cooper wrote in her 1998 book Air Conditioning America: “When the temperature plus 20 percent of the humidity reached 100 or more, everyone gave up and went home.”

That happened with some frequency in places like swampy Washington, DC. Those who didn’t need to clock in left the city entirely during warmer months, decamping for summer homes in the countryside. Lawmakers did too, vacating the District in June and returning in the autumn — a much-mourned political tradition that began to fade after air conditioning was installed in both houses of Congress in 1929. The White House and other government facilities soon followed, as the General Services Administration began incorporating AC into into New Deal-era federal office buildings, making DC what was likely the most air-conditioned city in the world at the end of the 1930s.

To encourage more employers to follow suit, the nascent HVAC industry showed off 1946 studies indicating that typists transferred to air-conditioned offices boosted their output by 24%. Efficiency and productivity, rather than personal comfort, became the technology’s big selling point, and trade publications touted surveys showing that workers preferred artificially cooled and filtered air, even in places with mild climates. “It is a great help to non-smokers who must work between inveterate smokers all day,” one worker in a Minneapolis office enthused in 1937.

A run of hot summers in the early 1950s further helped convince property owners and local officials that AC was a must for offices, hospitals and public buildings. The record-shattering 1954 heat wave in the Midwest forced authorities in St. Louis and Kansas City to close offices and postpone meetings and trials. Sales of portable window-unit air conditioners — then a new consumer product — surged.

A pattern emerged: Once about 20% of a city’s office buildings adopted AC, the rest were obliged to follow in order to compete, according to Cooper. As retrofitting systems into existing buildings was costly, postwar commercial structures began to be designed around artificial ventilation and lighting. That brought on the kinds of office buildings we now recognize as a universal standard: block-sized high-rises with sealed windows and vast floor plates, since workers no longer needed access to an open window for air and illumination. Such structures swiftly dominated cities, regardless of the local climate, as they proved cheaper to build per square foot than their naturally cooled predecessors.

With their glass curtain walls, these buildings were also prone to massive heat gain, demanding even more air conditioning; once manifested, the technology created the conditions for its own indispensability.

As it reshaped architecture, AC also reshaped the nation, reversing the post-Civil War migration from the southern US. Suddenly, working in Sun Belt cities became more appealing, and glassy towers rose in the downtowns of Atlanta, Dallas and Phoenix.

“By the mid-1970s air conditioning had made its way into more than 90 percent of the South’s high-rise office buildings, banks, apartments, and railroad passenger coaches,” wrote University of South Florida historian Raymond Arsenault in his 1984 paper “The End of the Long Hot Summer,” which chronicled the region’s embrace of AC and how it set the stage for the emergence of the urban South. By untethering the built environment from the sultry climate, artificial cooling constituted an “assault on the South’s strong ‘sense of place,’” Arsenault said, noting the current homogenous landscape of climate-controlled tract homes, chain stories, shopping malls and office buildings. When it comes to destroying local character and traditions, he concluded, “General Electric has proved a more devastating invader than General Sherman.”

The indoor environment that today’s office workers have inherited is roiled by its own issues — including debates over the gender inequities in thermal standards, concerns about the huge amounts of energy required to make office buildings habitable, and complaints about Europe’s AC habits. Behind our non-opening windows, those of us who enjoy manufactured weather on the job are effectively sealed off from the cooling gap between indoor and outdoor workers, and between well-off countries and the rest of the world. In India, less than 10% of the population has access to AC.

Technology may come to the rescue, again, with future advances in energy storage and carbon reduction. But there will be no going back to some pre-air-conditioned idyll.

More than just expectations have changed, Tulane’s Campanella notes: Cities like New Orleans are experiencing hotter temperatures in recent years in part because of a more pronounced local urban heat island effect as well as development patterns that devoured heat-mitigating greenery and wetlands.

The same AC-equipped buildings that shelter tenants from extreme temperatures also block breezes for others and pump out more heat. It’s a cycle that stands to turn the air-conditioned office — a rare American extravagance a century ago — into something more like a global necessity.

David Dudley is the author and editor for CityLab in Baltimore