And the same is basically true if you bought in 1966. What this tells me is that the Dow Jones (or stock market in general?) is not a good indicator (or even proxy) of wealth. Because GDP obviously grew immensely in both 30 years periods.
Based on this [1] calculator, you'd break event by 1940.
"Although it is one of the most commonly followed equity indices, since it only includes 30 companies and is not weighted by market capitalization and is not a weighted arithmetic mean,[citation needed] many consider the Dow to not be a good representation of the U.S. stock market and consider the S&P 500 Index, which also includes the 30 components of the Dow, to be a better representation of the U.S. stock market." - https://en.wikipedia.org/wiki/Dow_Jones_Industrial_Average
* https://www.inquirer.com/philly/business/vanguard-sp-500-ret...
* https://www.marketwatch.com/story/vanguard-employees-wont-ha...
It's literally adding up the prices of 30 stocks and dividing by a divisor that's been adjusted over time as stocks are added and removed from the index. It was easy to calculate early on, and it's continued because it's famous.