Historical data for the S&P 500 index is available on MarketWatch and Yahoo! Finance. Either site offers easy-to-use formats for accessing the data based on the entire index or individual stocks within the index.
To access historical data on MarketWatch, click on the site’s home page, and then click on Historical Quotes, enter the desired date, and press Set. Historical information available includes opening prices, daily highs, daily lows and closing prices for the selected date.
Yahoo! Finance offers a date-range function with drop-down menus for the start and end dates of desired historical prices. Historical pricing is available back through 1950, and information can be delivered in daily, weekly, monthly or dividend-only formats.