Toronto also had an elaborate security plan when it hosted the G-20 conference two years ago.
ABC7's Paul Meincke went to Canada's largest city to get a sense of lessons learned in the Toronto experience.
The policing challenge in Toronto was - as it will be in Chicago - protecting the visiting dignitaries while allowing large numbers of people their right to peaceful protest.
Toronto knew going in it would not be easy. And it wasn't. Because among the protestors were people who had no intention of expressing dissent in peaceful fashion. Some were home-grown. Others came from out of town to visit, and basically break things.
By some estimates there were 10,000 protesters in Toronto. They were not pleased that the main designated protest zone was a park almost two miles from the summit meeting site.
Police had met with some protest leaders in advance, knew of their plan to march, and allowed it.
Interspersed in the crowds were groups of so-called "black bloc" protesters - largely young men in their teens and 20s - dressed in black.
The march on Saturday afternoon of the summit weekend was noisy and tense, but initially non violent.
"Suddenly a flare went up, and all these black bloc tactic people started running the other way, so the parade went this way, the black bloc went that way," said Austin Delaney, CTV reporter.
What followed was extensive property damage carried out by a comparatively small number of people, described by police and others as hooligans with no agenda other than to create chaos. At varying points, they'd shed their black clothing and meld themselves back into the crowd.
"They'll change into their clothes, dump their clothes and then run back into the group. And that's what we saw, and we said to them, hey what are you doing?" said Delaney.
A couple of the young men caught on camera complained to Delaney that he and his photographer were invading their privacy.
Storefronts with breakable glass appeared to the opportunistic targets along with several squads - left by police and later torched.
"People were getting their pictures taken and putting on Facebook, kicking and spray-paiting and smashing and jumping on hoods," said Kevin Parker, Toronto merchant.
Critics say the initial police response was tepid at best. Their main focus was ensuring the security of the summit perimeter which they achieved. But the following day, police were far more aggressive, making hundreds of arrests and holding people in a former film studio converted into a mass detention center.
"We have some serious concerns about who they were arresting, why they were arresting, and whether they were just rounding people up," said Abby Deshman, Canadian Civil Liberties Assocation.
"Demonstrations are messy, they're not neat and tidy. People don't wear signs that identify themselves as reasonable protestors and violent anarchist," said Mark Pugash, Toronto Police.
Police contend that they accomplished their main mission. The perimeter was not breached. The dignitaries remained safe. In all this, there were no fatalities.
They do acknowledge - from initial strategy to the weight of riot gear front line officers wore - that they weren't agile enough - particularly when those bent on causing damage can coordinate so quickly with cell phones and social media.
"This is a serious challenge for law enforcement, to be mobile and flexible enough to deal with people who are dealing with the latest technologies to facilitate their violence," said Pugash.
Toronto's Police Department is strongly invested in the use of social media, and that will clearly be a big part of the policing equation in Chicago in May.
If the intent of some of the protesters is to create sporadic, hit-and-run violence on a widespread basis, then police have to be prepared to engage on multiple fronts, and that would likely mean having plainclothes police within the ranks of protesters.
Chicago's police superintendent says he's not commenting on specific tactics, but has said repeatedly that police will pursue protestors who are clearly breaking the law.