I remember our first window unit. It was York that my father bought in 1950. There is little or no difference in that old York then in a unit you would buy today.
Only today, they are a bit smaller and lighter.
About 10 years ago, the Building Museum in DC had an exhibit on air conditioning in America. I guess it had never dawned on me, but far from being a luxury, without air conditioning we would not have developed our manufacturing base. Between workers getting too hot to function and chemicals and processes that need a certain temperature, there is a lot that depends on having air conditioning.
I felt like a total nerd for going to the exhibit, but it was very interesting.