Many financial websites provide historical stock index data, explains Investopedia, including the Finance section of Yahoo.com. Companies that manage stock indices often list historical data as well. DJindexes.com and SPindices.com list historical data for Dow Jones and S&P stock indices, respectively.
To find historical data on Finance.Yahoo.com, search for the required stock index using the search bar, or click one of the popular indices, such as the Dow or S&P 500, that are listed at the top of the page. On each index page, click the Max link under the index chart to see the longest range of historical data available, or click the Customize Chart link to select a specific date range.
Finance.Yahoo.com also provides many extra options on its charts, such as the Simple Moving Average, Money Flow Index and Relative Strength Index. Find these options under the Indicator dropdown menu. The range of historical data varies depending on the specific stock index. For instance, Finance.Yahoo.com provides Dow Jones data back to 1985, but S&P 500 gives data all the way back to 1950, as noted by the companies.
Stock-index company websites, such as DJIndexes.com and SPIndices.com, usually list major indices on their home pages. Click on the desired stock index or, if necessary, search for a specific index using the search option at the top of the page. As of 2015, DJIndexes.com and SPIndices.com list up to 10 years of historical data.