Which US stock index reached its pre-crash peak on 3 September 1929?

The Dow Jones Industrial Average reached its pre-crash peak on 3 September 1929, shortly before the Wall Street Crash began.

The Dow had risen dramatically during the 1920s, reflecting enthusiasm for industrial companies, consumer goods, automobiles, and easy access to margin credit. Its September peak was followed by a period of volatility, then the catastrophic October declines commonly associated with Black Thursday, Black Monday, and Black Tuesday.

The crash did not by itself cause every aspect of the Great Depression. Falling investment, bank failures, debt deflation, reduced consumption, and policy responses all contributed to the prolonged economic collapse. The stock-market decline nevertheless became its most recognizable financial symbol.

The Nasdaq Composite did not exist in 1929; it was created in 1971. The S&P 500 also did not yet have its modern form. That makes the Dow the appropriate index for this specific historical peak.