Workers in office buildings throughout the country went home from their jobs in the hours after Tuesday's attacks on buildings in New York City and Washington, D.C. Many large buildings in U.S. were evacuated by midday, and several landmarks were closed.
In the Midwest's largest city, Chicago, midday Tuesday almost resembled the afternoon rush hour. Extra trains were put into service to carry home thousands of workers who left their offices early. Among the buildings evacuated - the Sears Tower. It is the tallest building in North America and a workplace for about 10,000 people.
The Art Institute of Chicago closed early, as did the city's aquarium and the Field Museum of Natural History.
The Chicago Board of Trade Building shut down, and trading was suspended at the Chicago Mercantile Exchange. Employees were told to leave.
In St. Louis, the trademark, 192-meter-tall Gateway Arch was ordered closed. By midday, the Arch's grounds were devoid of visitors.
Many major U.S. shopping malls were also closed in the aftermath of the attacks, including Mall of America in Bloomington, Minnesota - the country's largest shopping center.
In Detroit, the tunnel and bridge connecting the United States with Windsor, Ontario were closed for about an hour around midday. They reopened under tighter security.
The glass skyscraper along Detroit's downtown riverfront, which houses the headquarters of General Motors, was evacuated. However, GM says the company's auto plants remained open
In Michigan's capital, Lansing, many offices remained open, but security was noticeably tighter. Cheryl Speers works in a state government office building.
"We have to wear our badges to get back in," she explained. "I noticed there are police walking around the capitol and up and down the street. It is kind of nerve-racking."
Also in Lansing, evening classes and activities were cancelled at many area schools and community centers. One local television station ran a long list of churches in the area that were planning memorial services for the victims of the attacks.