These previous answers aren't uniquely about air conditioning, but they do touch on the evolution of clothing throughout the 20th century - /u/mimicofmodes on Why is historical clothing so complicated and another by them on JFK and the 20th century's casualisation of clothing, and finally this response on the difference between casual and formal clothing.

For more about office workers being hot and the change in office design over time, see this answer by /u/pooski.

A poorly-phrased question indeed, but this answer by /u/The_Alaskan touches on some primary sources from America in the 1700s (notably not about offices).

I work HVAC installation. Both commercial and residential.

Residential air conditioning wasn't widespread until the 70/80's but there were many commercial systems in place prior to that. I've had the absolute pleasure of working on some commercial systems that were designed pre-1950's.

The very first rudimentary system was created in the 1840's by Dr. John Gorrie to cool hospital rooms.

In the 1840s, physician and inventor Dr. John Gorrie of Florida proposed the idea of cooling cities to relieve residents of "the evils of high temperatures." Gorrie believed that cooling was the key to avoiding diseases like malaria and making patients more comfortable, but his rudimentary system for cooling hospital rooms required ice to be shipped to Florida from frozen lakes and streams in the northern United States.

To get around this expensive logistical challenge, Gorrie began experimenting with the concept of artificial cooling. He designed a machine that created ice using a compressor powered by a horse, water, wind-driven sails or steam and was granted a patent for it in 1851. Although Gorrie was unsuccessful at bringing his patented technology to the marketplace -- primarily due to the death of his chief financial backer -- his invention laid the foundation for modern air conditioning and refrigeration.

Eventually Willis Carrier took on the task and Carrier equipment came to life. By the early 1920's theaters and other large spaces were being cooled, the systems just too large and too expensive for residential applications. It required a large amount of square footage to condition the air in a large building, and still does today. Control components have gotten smaller over the decades, especially when the change from relay logic to Processors/PLCs came into play. You're still dealing with a lot of equipment though.

Cinemas were actually one of the first businesses to see air conditioning, but it wasn't as efficient as it is now. So you'd end up with hot spots, muggy spots and cold spots.

Now keep in mind, when you think of air conditioning a large commercial building, you're not necessarily dealing with a system like you deal with in a residential setting.

To explain it very basically. In a residential system, you have an air handler with a coil in the house. The air passes through the indoor coil,water drops out and heads to a drain. Refrigerant is used to keep the indoor coil cool. After the refrigerant gets warmed by the passing of air through the indoor coil, it's sent out to the outdoor coil, where it's cooled and compressed, then sent back into the indoor coil. Repeat that the entire time the cooling system is running. This is a very basic description.

All of that is run through your existing furnace, and your outdoor unit that takes up a small area in your back yard. Things are changing though, and we're definitely headed towards a future where heat pumps are going to be the main way to heat and cool your home, some people in some areas already use them. They're becoming infinitely more efficient, and replacing gas/propane/fuel furnaces.

When you get into a commercial system, the game changes a bit. One company I worked for still serviced a large scale - cooling system that was installed in the late 1940's for a very old building. It still worked well, and replacement would have cost a ton. So they just upgraded/repaired systems as needed.

I am going to use that system as an example. The building had a cooling tower on the roof. Water replaces what the refrigerant does in a residential system.

So basically what happens is, cool water charges a coil, warm air passes through the coil and is cooled, the water warms and then is sent to the cooling tower on the roof. In this system the water was dropped past a cooling fan, collected and then sent back through the system.

Rather than taking up just small spot in your basement/backyard, this system required a full floor. Pumps, treatment systems, coils, fans and more pipes than you could shake a stick at, that were improperly labeled when we took the job over and evidently I was supposed to know that. (That's a different post)

The benefits of this system was energy consumption. It just used fans, coils and water. There was no refrigerant that condensed/compressed. The cons of this system is that cooling isn't as great as it could be, but it was good enough for that building, which was largely storage with a few offices. Another con was water consumption. While the system was "sealed" evaporation still occurred and the system had to be topped off. If the system had to be drained and refilled, it would have been extremely costly.

"Air conditioning" is also a broad term that encompasses many different types of heating and cooling. In some older buildings in my area, the cooling system just moves large volumes of air using fans to cool the air. That system looks to turn over fresh air x amount of times per hour throughout the building.

In other buildings, there are commercial sized systems that use refrigerant like a residential system does. (Just different type of refrigerant) There is also evaporative cooling that is good for low humidity regions, along with geothermal heating and cooling. That's just a small list.

Even just in the United States, there are different regions where one type of air conditioning would be horrible to use compared to another region. An evaporative cooler in a high humidity region, like where I live, would not be beneficial because it adds humidity to the air. That would be more beneficial in a dry area, like Nevada or California. The United States has everything from deserts to swamps, so how a building is cooled/heated changes depending the location.

It also depends on the shape of the building. Tower-style buildings can be different than warehouse style buildings. In a warehouse setting it isn't odd to see multiple or even dozens and dozens of roof top units (using coolant like a residential system) cooling different zones of the warehouse.

The Evolution of Air conditioning (PDF Warning) published by ASHRAE (The American Society of Heating, Refrigerating and Air Conditioning Engineers) is about how Ventilation and Air conditioning evolved in an office setting and may be of some interest to you.

So when someone went to an office in 90 degree weather, they probably weren't dealing with 90 degree temperatures. The air was by no means conditioned as well as it is today, but there were definitely systems in place to keep air ventilated and cool. Back then they still had the option to open windows too, which isn't an option in most modern buildings.

I hope this helps and meets the standards of the sub, I usually just lurk here.