Somewhat related question: where/how did you acquire that data? I have been meaning to run some simulations on the S&P 500 historical daily closing data, but I

Somewhat related question: where/how did you acquire that data? I have been meaning to run some simulations on the S&P 500 historical daily closing data, but I can't seem to find a place that provides the data covering for the last 40-50 years. Thanks in advance for your answer!