If we have learned anything in the last five years, it is this: one man's symbol of prosperity could be another man's target. And in Chicago, the heartland's largest city, there are plenty of targets.
"We have the Sears Tower, we have a thriving financial market, we have a city that looks great," says Cortez Trotter, whom Mayor Richard Daley appointed last April to become the city's first-ever chief emergency officer.
Correspondent Erin Moriarty reports on how the city is using cameras and other methods to keep its citizens safe.
While most Americans don't want to think about potential disasters, Trotter thinks of little else. "It's something (that) a.) you don't take lightly and b.) you go home at night thinking, 'I've got to do better. I've got to do more,'" Trotter explains.
There are a number of new security measures that have been added to make the city safer.
On the streets of Chicago, you probably won't see the cameras. But these days, more and more, someone is probably watching you.
"We have people watching all types of things that 10 years ago, we might have thought there was nothing unusual about it," says Trotter.
"Operation Virtual Shield" may be the most extensive city surveillance system in the country, linking about 3,000 cameras, some of which can zoom in so close, they allow authorities to read license plate numbers.
"We've got them spaced every two blocks," Trotter explains.
"Now, if that truck is sitting there an hour from now, maybe what we should do is have a police squad car go by and just check why this truck that's been sitting for an hour is still sitting there," Trotter tells Moriarty during a demonstration of the camera system.
And more than 100 private companies are also connecting their cameras to the system. "Of course Sears is on that list, Boeing is on that list, John Hancock is on that list. What we're doing is taking their cameras and feeding them right into our system here," Trotter explains.
Chicago has had a head start over most cities – in 1995, Mayor Daley had a vision of putting police, fire and emergency responders into one building. The project cost $217 million.
"I said, just build me something that we know is gonna last. And, basically technology would change. It was controversial. Someone said it was a waste of money," Daley says. "And unfortunately, when 9/11 came, 'You're a genius.'"
It is considered state of the art. But there are still large holes in this "virtual shield."
For example, there is no screening of passengers getting onto commuter trains. Pre-screening passengers is impractical, says mass transportation expert Joe Schofer.
Yet, while the federal government spends about $8 per passenger for aviation security, only four cents per passenger go towards rail safety.
"I think it's disproportional," says Schofer.
Chicago's Metra and other rail lines use bomb-sniffing dogs, but as an undercover investigative report in February by CBS station WBBM pointed out, they are not foolproof. An investigator carrying a bag with components of gunpowder walked by one of these dogs; there was no reaction, not even when the bag was put right in front of the dog.
The kind of terrorism that seems to worry security experts most is bio-chemical and Chicago has already had a close call. Just six months after 9/11, a man was found in a subway tunnel with the ingredients for cyanide gas. Joseph Konopka — who called himself "Dr. Chaos" — had no apparent political agenda. He is now in federal prison.
"How many areas can we be hit by terrorism? Probably more than we could ever protect," says Trotter, who admits no city can prevent all attacks, which is why the response is just as critical.
In Chicago, detailed floor plans of all major buildings are available to all emergency services. Using the 22nd floor of the Sears Tower as an example, Trotter explains, "The responding units then know that there's potentially 100 people on that particular floor."
"We have not only the floor plan, but the actual evacuation procedure on each and every one of those buildings," he adds.
Former Illinois Gov. Jim Thompson, who sat on the 9/11 commission, says he would give Chicago a B for achievement and an A for effort.
Thompson says Chicago – like all American cities — may still have problems with communications among rescue workers.
"The Congress agreed to turn over radio spectrum to first responders so that the police and fire can talk to each other, as they were not able to do in New York. But when do we turn it over? 2009. Why 2009? Why not now?" asks Thompson.
Trotter says he often thinks of 9/11.
"I watch the video of it often because it keeps me focused," he says. "As I see the faces of the public as I walk on the street and we're responsible for them. And I want them to go on living their lives and feeling comfortable knowing that at night or early in the morning, I'm doing enough worrying for everybody."