The article says "total return", and the price index only increased by 513x (from 68.63 to 35,208). so I'm pretty sure they're including dividends.

True. I missed that. The calculator at [1] gives totally different returns with dividends reinvested, though: 7.6%.

[1] https://dqydj.com/dow-jones-return-calculator/

I am including dividends.

I sometimes wonder if there are some long forgotten brokerage accounts just idly compounding.

There aren’t, actually, at least not in the US. When an account has no activity on it for long enough, it gets liquidated and transferred to the state until someone with a rightful ownership claim comes forward to claim it. This is called “escheatment.”

https://en.wikipedia.org/wiki/Escheat

Though dividends paid in cash don't really count as compounding no?

You can reinvest them it or he stock after you’ve paid income taxes on them.

I'm pretty sure they use a price that accounts for dividends. Or they should anyway unless they're doing it wrong.

Compounding works best when dividends are immediately reinvested... it also pushes up the total return considerably.