The S&P 500 was officially created in 1957, but its origins date back a little further to 1923. Back then it wasn't quite the S&P 500, it was a smaller index.
When the series first started, it included 233 companies and covered 26 industries.
Fast forward 30 years to 1957 when the S&P 500 expanded into the largest 500 companies in the world.