IIRC this book covered the history pretty well.
Tl;dr - after WW2 the auto manufacturers asked the unions for a deal to guarantee no strikes. Too much money to be made selling cars/trucks to devastated countries. The deal the unions and big auto struck was the basic modern package - 2 weeks vacation, 9-5 M-F, medical, pension. Everyone else had to match, because big auto and associated suppliers were hiring everyone.
By the 70s whole thing went sideways as big auto moved overseas. But the US culture had adopted a lot of it since as basic minimum.
IMHO it’s been pressure downward on workers ever since, with a few notable areas like tech and now the big shifts due to Covid, boomer retirement, etc.
The Big Squeeze https://www.amazon.com/dp/B0017L8N6O/ref=cm_sw_r_cp_api_glt_74DGNTE01E0MMC9Z60B4