And the bond market exchanges observed a minute of silence at 8:46 a.m., when the first plane hit the World Trade Center, and another minute of silence at 10:29 a.m., when the second tower collapsed. Bond markets closed early today at 2 p.m.
Financial Firms Remember
In addition to the exchanges, many financial firms, some of which were in or near the towers, will observe the day with moments of silence, providing counseling for employees and flexible attendance policies.
Cantor Fitzgerald, which lost 658 employees, did not open its U.S. offices. It was planning to hold a private memorial service at 4 p.m. in New York's Central Park.
"It is important that our employees have the opportunity to be with each other and their families on the anniversary of the tragic events of Sept. 11," said Cantor Fitzgerald Chairman and CEO Howard Lutnick, whose brother was among those killed in the attacks.
Investment bank Sandler O'Neill, which lost 66 of its workers, held a memorial service at its offices at 9 a.m., with three clergy members who presided over a service the firm held last October. The firm opened for business with the markets.
Merrill Lynch, which is headquartered at World Financial Center, next to the trade center site, had a ceremony for employees in the morning, followed by a moment of silence at 8:46 a.m.
The company dedicated plaques for all who perished in the attacks and for the three Merrill Lynch employees who died, and it also displayed flags of the armed forces that were raised at the company's building last year.
Silence, Understanding Across the Nation
Outside of New York, other businesses also opened late and allowed many employees to stay home in observance of the day.
Discount retailers T.J. Maxx and Marshalls, for instance, observed a minute of silence before opening their stores at noon. Memphis, Tenn.-based FedEx Corp. made counselors available and paid workers to volunteer for the day. FedEx expected some 30,000 of its employees to volunteer today with the United Way.
Microsoft was open for business, but allowed employees to take the day off if they needed it and did not advertise during the day. Other companies like UPS, Target, Sears and the Big Three automakers are also refraining from broadcasting commercials today.
Meanwhile, the airline industry came together to honor their lost crew members who died in last year's attacks with a ceremony in the nation's capital. And aboard a Chicago-to-San Francisco flight, the captain called for a moment of silence at the same time of day the first jet crashed into the World Trade Center.
Elsewhere, many of the nation's telemarketers will be taking the day off. The Direct Marketing Association, the industry trade group that represents telemarketers, has urged its members to either refrain from conducting unsolicited e-mail and telephone-marketing campaigns today or conduct their campaigns "with the utmost caution and respect."
ABCNEWS' Gena Binkley, Ramona Schindelheim, Steve Scott and Catherine Valenti contributed to this report.