What is the S&P 500?

The S&P 500 is a stock market index tracking 500 of the largest publicly traded U.S. companies, weighted by market capitalization. It is widely considered the benchmark for overall U.S. stock market performance. The index is maintained by S&P Dow Jones Indices, which periodically adds and removes companies. Investing in an S&P 500 index fund gives you ownership stakes in all 500 companies at very low cost.