180 AD: A Chinese inventor named Ding Huan made a room-size fan from seven wheels (each three meters wide) that was so effective "people would even begin to shiver."
3rd century AD: Roman Emperor Elagabalus constructed a mountain of snow, fetched from the nearby peaks by a train of donkeys, to cool his gardens.
1881: Naval engineers built a contraption housing bedsheets soaked in ice water, with a fan that blew hot water overhead, to cool down a dying President James Garfield. Though the method lowered the room's temperature by 20 degrees, it required half a million pounds of ice over the course of two months.
1902: One year after graduating from Cornell University in engineering, Willis Carrier was working at the Buffalo Forge Company, a printing house, for $10 a week. The 'Apparatus for Treating Air' (patent # 808897) that he invented was meant to eradicate the humidity that warped the paper used in the factory.
1911: Carrier later perfected the "Rational Psychrometric Formulae" that still governs the mechanics of A/C units today, as well as a centrifugal refrigeration machine (1921) that worked in large spaces. Once he figured out how to replace the toxic coolant ammonia with the much safer coolant dielene, it was safe for public use, like the J.L. Hudson Department Store in Detroit, Michigan—the first apparatus installed in a U.S. department store.
1930s: Those not fortunate enough to stay in luxury hotels and drive private cars likely first encountered modern air conditioning in movie theaters, which became commonplace by World War II.
1971: Central air conditioning is added to Chicago's Sears Tower, then the tallest skyscraper in the world.
1979: TIME columnist Frank Trippett laments Americans' by-now slavish devotion to artificial cooling. "It is no exaggeration to say that [they have taken to it avidly and greedily," he remarked. "Many have become all but addicted."
2012: Carrier's eponymous company is now installing the HVAC system at... the Sistine Chapel!

Now that modern home dwellers are, more than ever, focused on sustainability, how do you imagine the future of air conditioning?