Data on major stock indices is not currently available on IEX Cloud
Data on the S&P 500, Dow Jones Industrial Average, and other major stock indices is not currently available on IEX Cloud and is unlikely to be in the near future.
Pricing for this data is typically high and requires a direct contract between each consumer and the index provider regardless of who actually supplies the data. For instance, the major index providers charge over $10,000 a year for delayed data.
An alternative is to display ETFs that match those indices, such as SPY for the S&P 500, DIA for Dow Jones, and IWM for Russell 2000.