Here you can download free data of the S&P 500 from 1789 until today (for Excel, in format: Daily, Weekly, Monthly, etc.):
write at the top left (in the box: Symbol np): ^SPX and then click on: Kwotuj
and then click at the bottom left on: Historical data
choose Interval: Daily, Weekly, Monthly, etc...
click at the bottom on: Download data in csv file
write at the top left (in the box: Symbol np): ^SPX and then click on: Kwotuj
and then click at the bottom left on: Historical data
choose Interval: Daily, Weekly, Monthly, etc...
click at the bottom on: Download data in csv file