I think it's worth noting that S&P 500 index funds didn't exist until the 70s. You'd be spending a lot of time and money to approximate it before that.
So at the £5ish/trade of my current broker, that's a cool £912500/year on just commission.
For some reason the massively reduced ease of entry to a trading strategy like this is never considered when lauding its historical performance.
Modern S&P500 funds like SPY or VOO rebalance quarterly FYI