Below is a chart of the Dow Jones Industrial Average (DJIA); note the total percentage gain over the past 105 years: 39249.36%.
A $10,000 investment in the DJIA index (ticker symbol: DIA) 105 years ago is worth to $3.4 million today. A 39249.36% increase, (373.80 percent annual rate of return).
Over the past 30 years, the DJIA has increased 1254.22% (a 41% annual rate of return - better than Warren Buffett's 65-year career average of 23%). A $10,000 investment in the Dow Jones 30 years ago is worth $135,400 today.
Looking at it a different way, a $100,000 investment in the Dow in 1988—say, at the age of 20—is now worth $1.4 million and you're now a 50-year-old millionaire with an option to retire early.
DJIA 30-year (1988 - 2019) performance (%):
The point here: U.S. stocks make good long-term investments.