On the FRED web site
I constructed the following graph which shows the S&P 500 Index in both nominal terms (blue)
and adjusted for the changes in the non-seasonally adjusted CPI-U (red)
. It looks like the inflation adjusted value peaked around the year 2000.
The graph starts January 1957 when the CPI-U
was 27.6. Click the graph to bring up a screen where you can edit it. (For example, you can start the graph later than 1957.)
Edit: I changed the base CPI from January 1957 = 27.6 to March 2000 = 171.2. Before, the adjusted line had so little vertical scale that its changes were hard to see. This change makes it easy to see how far we are from the inflation-adjusted high set in 2000.