The first modern air conditioner was invented in 1902 by Willis Haviland Carrier, a skilled engineer who began experimenting with the laws of humidity control to solve an application problem at a printing plant in Brooklyn, NY
I'd agree it became more widely spread in the 50s.
At the St. Louis World's Fair in 1904, organizers used mechanical refrigeration to cool the Missouri State Building. The system used 35,000 cubic feet of air per minute to cool the 1,000-seat auditorium, the rotunda and other rooms within the Missouri State Building. It marked the first time the American public was exposed to the concept of comfort cooling. A big breakthrough in comfort cooling technology came in the 1920s, when Americans flocked to movie theaters to watch Hollywood stars on the silver screen.
Early cooling systems for public theaters were essentially heating systems modified with refrigeration equipment that distributed cold air through floor vents, resulting in hot, muggy conditions at upper levels and much colder temperatures at lower levels, where patrons sometimes resorted to wrapping their feet with newspapers to stay warm. In 1922, Carrier Engineering Corporation installed the first well-designed cooling system for theaters at Metropolitan Theater in Los Angeles, which pumped cool air through higher vents for better humidity control and comfort throughout the building.
