The city's vast network of surveillance cameras is being closely watched, and metro Chicago's transit systems, airports and religious buildings are all receiving extra law enforcement attention.
The measures follow a joint bulletin Monday issued by the FBI and Department of Homeland Security warning of possible attacks on the U.S. to avenge the killing of al-Qaida founder Osama bin Laden.
After years as the FBI's most-wanted terrorist, the red deceased banner has finally been added under bin Laden's name.
Chicago Mayor-elect Rahm Emanuel was still White House Chief of Staff last August when the first lead pointed to Osama bin Laden living in a compound north of Islamabad, Pakistan.
"A lot of people's lives were lost along the way to get to this point," Emanuel said Monday. "They have to be remembered, they have to be recognized - both people in the Armed Forces, men and women in the intelligence community who never gave up, never gave in even when it was in darkest moments, and to the president and his national security team for being aggressive in their pursuit of this."
On Monday, University of Chicago terrorism researcher Jenna Jordan said there could be a flip side to bin Laden's death.
"What my data shows is that against these types of organizations - older groups, larger groups, religious groups - targeting their leader actually can increase their resilience and increase their lifespan overall," said Jordan.
Police in Chicago Monday night said they are keeping a close eye on street security cameras and known targets, including the Willis Tower, the tallest building in the United States.
At the United Center, fans arriving for the Bulls playoff game were searched for weapons.
If authorities in Chicago are on edge, it may be for good reason, according to DePaul terrorism expert Tom Mockaitis, who wrote a biography of bin Laden last year.
"We are an untouched, an untried target in that regard, and that gives us some attraction," said Mockaitis. "We're a hub, which means a lot of things come and go through here."
Even though a crash cover of Time magazine puts a big red 'X' over bin Laden, Mockaitis says it may be too early to call an all-clear on the threat from al-Qaida.
"I'm worried about the death by a thousand cuts kind of thing, where you stage of series of smaller ones, similar to what was done in Mumbai, where a team of ten kept a city hostage for about 60 hours," said Mockaitis.
Federal authorities say bin Laden was identified by DNA comparison to several relatives. Survivors on the scene identified him, and photos were matched through facial recognition scans.
Pictures and video from the assault also exist, as several Navy SEALs were wearing helmet cameras, and bin Laden's burial at sea was taped.
