PORTLAND, Oregon (AP) ― John J. Phelan Jr., the former New York Stock Exchange chairman credited with managing the chaos of the “Black Monday” market crash of 1987, died Saturday. He was 81.

The NYSE Euronext and Phelan’s family confirmed his death Monday. The cause of death was not disclosed.

A former Marine who worked as trader for years before leading the exchange, Phelan was best known for keeping the markets open following the historic crash on Oct. 19, 1987. That day, stocks suffered what is still the largest single-day percentage drop, with the Dow Jones industrial average crashing nearly 23 percent.

It was considered Phelan’s finest moment. Those who were there say panic gripped Wall Street as trading volumes soared, orders littered the floor and the Dow plunged.