History of S&P 500 in Timeline

The S&P 500 is a stock market index that tracks the performance of 500 leading publicly traded companies in the United States. Representing about 80% of the total U.S. market capitalization, it serves as a key indicator of overall market health. As of January 2024, the aggregate market cap of the companies within the index exceeded $43 trillion. The index is widely followed by investors and analysts as a benchmark for U.S. equity performance.

1860: Formation of Poor's Publishing

In 1860, Henry Varnum Poor formed Poor's Publishing, which published an investor's guide to the railroad industry.

1906: Standard Statistics Bureau Founded

In 1906, the Standard Statistics Bureau was founded, later becoming the Standard Statistics Company.

1923: Standard Statistics Company's First Stock Market Index

In 1923, Standard Statistics Company developed its first stock market index consisting of the stocks of 233 U.S. companies, computed weekly.

1926: Inception of the Index

Since its inception in 1926, the S&P 500 index's compound annual growth rate—including dividends—has been approximately 9.8% (6% after inflation).

1941: Merger to Form Standard & Poor's

In 1941, Poor's Publishing merged with Standard Statistics Company to form Standard & Poor's.

March 4, 1957: S&P 500 Expansion

On March 4, 1957, the index was expanded to its current form of 500 companies and was renamed the S&P 500 Stock Composite Index.

1962: Ultronic Systems Compiles S&P Indices

In 1962, Ultronic Systems became the compiler of the S&P indices including the S&P 500 Stock Composite Index, the 425 Stock Industrial Index, the 50 Stock Utility Index, and the 25 Stock Rail Index.

August 31, 1976: First S&P 500 Mutual Fund

On August 31, 1976, The Vanguard Group offered the first mutual fund to retail investors that tracked the S&P 500 index.

April 21, 1982: S&P 500 Futures Trading Begins

On April 21, 1982, the Chicago Mercantile Exchange began trading futures based on the S&P 500 index.

1982: Original SP Big Contract Started

In 1982, the original SP big contract began trading.

July 1, 1983: S&P 500 Options Trading Begins

On July 1, 1983, the Chicago Board Options Exchange began trading options based on the S&P 500 index.

1986: Real-Time Index Updates

Beginning in 1986, the S&P 500 index value was updated every 15 seconds, disseminated by Reuters.

January 22, 1993: S&P Depositary Receipts ETF

On January 22, 1993, the Standard & Poor's Depositary Receipts exchange-traded fund issued by State Street Corporation began trading.

September 9, 1997: S&P E-mini Futures Contract

On September 9, 1997, CME Group introduced the S&P E-mini futures contract.

2005: Transition to Public Float-Adjusted Capitalization-Weighting

In 2005, the S&P 500 index transitioned to a public float-adjusted capitalization-weighting.

September 17, 2021: Final Trading Date for Original SP Big Contract

Friday, September 17, 2021, was the final trading date for the original SP big contract which began trading in 1982.

October 2021: Allegations of Rating Purchases

In October 2021, Bloomberg News reported that a study alleged that some companies purchase ratings from S&P Global to increase their chances of entering the S&P 500 Index—even without meeting the full criteria for inclusion.

January 2024: S&P 500 Market Cap

In January 2024, the S&P 500 had an aggregate market capitalization of more than $43 trillion.

September 30, 2024: S&P 500 Top Companies

On September 30, 2024, the nine largest companies in the S&P 500 accounted for 34.6% of the index's market capitalization. These companies, ranked by weighting, were Apple, Microsoft, Nvidia, Amazon.com, Meta Platforms, Alphabet (Class A & C shares), Berkshire Hathaway, Broadcom, and Tesla.