As much as 80% of the illegal narcotics in America's third-largest city come from Guzman's Sinaloa cartel, said Art Bilek, a retired Chicago detective who spent 60 years in law enforcement.
"Guzman is the reason you've got kids fighting over just one corner, and shooting each other," he said.
Much of the gun violence in the city can be traced to drugs that come from Sinaloa, the region of Mexico where "El Chapo" was born to a poor rural family and rose to lead a global network of smugglers, dealers, assassins, corrupt politicians and paid-off police.
"Guzman has hurt everyone -- the users in the city and the suburbs, the innocent bystanders, the kids who get wrapped up in gangs," said Bilek, who ran the nonprofit Chicago Crime Commission, one of nation's oldest civic anti-crime organizations.
Sinaloa's Chicago-based loyalists, led by eccentric twin brothers who were Guzman's best traffickers, helped the cartel make billions of dollars by pumping multiple tons of their product -- heroin, methamphetamine, cocaine and marijuana -- into the city.
Jack Riley led Chicago's Drug Enforcement Administration office for years. Now the deputy administrator of the DEA in Washington, Riley told CNN that Guzman had an "ability to enter in partnerships, businesses, with nearly 150,000 street gang members who make their living putting heroin and cocaine and meth on the street."
Eighty-three percent of men arrested for crimes in Chicago in 2013 tested positive for drug use, according to the White House Office of National Drug Control Policy.
The kingpin's imprisonment over the years -- including his time in a Mexican prison from February 2014 until his escape Saturday -- did not abate the flow of drugs into the city, Bilek said.
"At this point [drug trafficking is] so well-established, it's part of the culture," said Bilek, who spent his career in the police department's organized crime unit, a division that increasingly, over the years, involved narcotics.
"The DEA and the FBI are working at their maximum and judges are giving strong sentences," he said. "It's very complex."
He doesn't have a solution. He's not sure there is one.
It isn't for lack of trying over the years. In 2009, Chicago's Department of Justice prosecutors indicted Guzman in absentia, charging him with conspiring to transport narcotics across international borders.
This week, Chicago Crime Commission members stressed that they wanted him extradited to the United States if he's caught.
He is public enemy No. 1 in Chicago, they said. The label has been given only once before, to Prohibition-era gangster Al Capone.
"Until Guzman is in U.S. custody and on U.S. soil, we [are] not going to remove the designation," said J.R. Davis, the commission president.
Guzman's reach into Chicago goes back to the early 2000s, said Jeffrey Johnson, the board director of the Chicago Crime Commission. Johnson told reporters this week that the Sinaloa cartel is the "underground UPS."
Chicago was a shrewd choice, logistically, for an entrepreneurial trafficker who wanted to control not just one city, but expand to points north, east and west, said Bilek.
Guzman's Chicago-based operation, according to court documents, was a supply point for Detroit; Milwaukee; Philadelphia; Washington, D.C.; Cincinnati and Columbus, Ohio; New York City; and even into Canada, to Vancouver.
He was able to pull this off for several reasons.
A large number of people from Mexico live in Chicago, and Guzman exploited that connection. The 2000 census showed more than 530,000 Mexicans residing in the city. "People have friends and relatives who go back and forth," Bilek said.
"There is an interchange, a community he could tap. It wasn't just people who wanted to. It was, in some cases, 'You do this or I hurt your family back home.'"
Guzman recognized he could take advantage of busy road traffic between Mexico and the Midwest. The drugs would be hidden inside large trucks and other vehicles coming through "every day, around the clock," Bilek said. "You send 10 trucks through, even if [inspectors] figured out they had a problem with one truck or two trucks, you were still good to go with eight getting through. It was a whole armada of cars and trucks and people on motorcycles, too."
But Guzman needed lieutenants in Chicago who could assure that those shipments reached high-level dealers, who would then disperse them to the low-level corner dealers who got the drugs into users' hands, or to the dealers who served the wealthier users in the suburbs.
Two hometown boys, Margarito and Pedro Flores, obliged.
Chicago twins turn on El Chapo
The Flores brothers were raised in Little Village
, a Mexican-American community on the West Side.
In 1981, their father, already convicted of smuggling people from Mexico, was caught in an undercover federal sting selling 11 pounds of heroin, according to the Chicago Tribune
, which has reported in depth about the siblings and their work for the Sinaloa cartel.
When the boys were 5 years old, one got into trouble with authorities because he was with teenagers allegedly firing guns from a car in Little Village, the newspaper reported. When the siblings were 10, authorities raided their house and found more than $190,000 worth of marijuana, the paper said.
Law enforcement believe they were well-established drug dealers by the 1990s, Bilek said. At some point they connected with Guzman, and they worked for him between 2005 and 2008. Within three years, they had moved more than 60 tons of cocaine, a court transcript shows.
"At that level, federal agents took notice," he said.
The brothers operated a wholesale cocaine and heroin distribution organization for Guzman, according to an indictment of Guzman and the brothers
. The cartel leader got cocaine from Central American and South American countries such as Colombia and Panama and smuggled it to Chicago, where the twins used several warehouses to unload and store the drugs, and parse the bulk into smaller amounts to be distributed throughout the United States.
Ledgers kept track of profits. Workers bundled cash in dryer sheets to throw off drug-sniffing dogs, and couriers smuggled the money back to Mexico.
The indictment says Chicago's Sinaloa operation maintained control by bribing corrupt public officials and threatening law enforcement, rival traffickers, people within its own network.
According to a portion of Margarito Flores' testimony
, which the Chicago Sun Times published
, the siblings received shipments of cocaine from points other than in Chicago. The coke was transported in tractor-trailers with hidden compartments, he said. Those compartments were used to smuggle part of the $1.8 billion the twins sent back to Mexico, according to the U.S. Department of Justice
Although we had customers in several cities," Margarito explained, "most of the time the cocaine that Pedro and I distributed in the United States at one time passed through Chicago."
Investigators were able to glean so much information because, after violence broke out between Guzman and a rival cartel leader, the twins became informants for the feds and went into protective custody in 2008, according to the DEA
Their guilty pleas to narcotics distribution conspiracy became public in November 2014, after they took a huge gamble -- they recorded phone conversations with Guzman in which the kingpin agreed to decrease the price of a load of heroin.
The Flores twins were sentenced in January to 14 years in prison.
District Chief Judge Ruben Castillo said he would have imposed a life sentence had they not cooperated.
The brothers, he said, "devastated the walls of this city."
Regardless, he observed, they were, in a way, "going to leave here with a life sentence" for betraying the world's most murderous cartel leader.
The twins are being held in secret locations.
But Guzman has ways, Bilek reminded.
The brothers' father was "kidnapped and presumed killed as a result"
of their cooperation with federal authorities, a defense attorney said in court during the Floreses' sentencing hearing.
Margarito and Pedro Flores are "marked men," Bilek said. "I would be surprised if he [Guzman] didn't take action against them. There's no rush, because the brothers aren't going anywhere.
"Guzman could kill them or their whole families. That's what he does -- kills babies to grandmothers -- doesn't matter. He is ruthless."