The decline of technological advancement
Paul Krugman’s review of Robert J. Gordon ‘s book The Rise and Fall of American Growth is very interesting. (And non-partisan: no attacks on Republicans or conservatives as Krugman often does.)
Urban life in America on the eve of World War II was already recognizably modern; you or I could walk into a 1940s apartment, with its indoor plumbing, gas range, electric lights, refrigerator and telephone, and we’d find it basically functional. We’d be annoyed at the lack of television and Internet — but not horrified or disgusted.
By contrast, urban Americans from 1940 walking into 1870-style accommodations — which they could still do in the rural South — were indeed horrified and disgusted. Life fundamentally improved between 1870 and 1940 in a way it hasn’t since.
I might also point out that the 1940s had cars and air travel (although air travel became significantly less expensive in the 1970s with the invention of large jet airliners like the Boeing 707; in the 1940s you probably would have flown on a Lockheed Constellation).