There was no S&P 500 in 1928, and 30s, and 40s. It started on 1

The real S&P 500 started on 1957.  The data before that can not be used for return purpose since the index was not 500 stocks.  It has very small numbers of stocks called 'Composite Index'.  But even 1957, it has 60 years data to use to calculate the returns.