S&P 500 · September 22, 1987

A bounce four weeks before the crash

+2.89%

single-day change vs previous close

Part of a longer stretch

The Black Monday slide

early in it · 1987-08-25 → 1987-12-04, -33.51% over the whole period

What happened that day?

22 September 1987 — the S&P 500 rose 2.89% to close at 319.50. No single cause can be pinned to the day
This episode was the decline that started at the late-August high. This was one up day inside it
The Fed had raised rates early in September, because of inflation and the dollar. That is unhelpful for equities
After it the index slid while swinging widely in both directions. This gain was one side of that swing
Four weeks later, on 19 October, this index recorded the largest one-day fall in its history
In hindsight days like this in September were not a bottom but the middle of an unfinished decline. That cannot be known at the time
From the late-August high to the 4 December low the index fell 33.51%

Sources

Every figure on this page is recomputed from the original daily closing prices and checked against them at build time. The account of what happened is put together from the public record; where a specific source was consulted it is listed above.