The Crash: Once Upon A Time in October . . .

As usual, there were dark portents. On Sept. 5, 1929, just two days after the New York stock market reached its highest level in history, an eccentric statistician named Roger Babson warned the National Business Conference that "sooner or later a crash is coming, and it may be terrific." The market responded nervously, with the New York Times's 25 leading industrial stocks taking a 10-point dip, then recovering. The Times fretted about the "idea of an utterly disastrous and paralyzing crash."

Also as usual, the portents went largely ignored. People yearned to believe what the authorities told them. Calvin Coolidge, on...