Usually when they compare labor force participation rates they only go back to around 1978 because generally we want to compare apples to apples jobs.
If you go back to the 1950s technically "women" weren't really in the workforce per se, as the majority of women working were young single women working temporary or part-time jobs, one of the most common jobs was "live-in nanny" like in the Brady Bunch. Men earned enough to support a family back then and there was no need for women to be co-bread earners. You can see while overall LFP may have been 59% in 1950, about 88% of men of working age were employed.
Edit: didn't realize blogspot images were banned here...