"I think the original announcement was like, "Oh no, what's gonna happen here,'" said Becky Rodgers of Neighbors in Strip Direct.
Two weeks before world leaders were to arrive, the Secret Service revealed two fairly tight security perimeters around the Lawrence Convention Center downtown. One that prohibited vehicular traffic and an inner perimeter with checkpoints for those with credentials.
Pittsburgh was keenly aware of what happened in other host cities.
"As the event got closer, I think folks got a little more uptight," said Pittsburgh Mayor Luke Ravenstahl. "But we knew we had a plan in place, and we trusted that plan and we executed that plan."
Bridges over the Allegheny River were closed and the river was patrolled by gunboats.
When the dignitaries arrived for their two day summit, downtown, Pittsburgh was largely empty of people who either couldn't get around or simply chose to stay away.
Jimmy Sunseri is a third generation food wholesaler in Pittsburgh's 22-block long strip district, home to an eclectic collection of largely mom and pop merchants and diners.
"Economically it crushed us," he said. "Crushed every merchant down here."
Business was so slow during the summit, workers wound up playing football in the middle of Penn Avenue.
There were protest marches, the largest of which crossed a bridge within sight and sound of the convention center. It was overwhelmingly peaceful.
There were pockets of trouble, some property damage, most of it caused by one person.
Pittsburgh used what's called a long-range acoustic device for crowd dispersal orders, and followed that with the machine's very high pitched audio blasts.
Overall there were 100-plus arrests, the fewest of any modern day global summit.
"We were prepared for more arrests, but we were fortunate we have very few," said Pittsburgh Public Safety Director Mike Huss.
So for Pittsburgh, two and a half years later, what's the takeaway from hosting the G20?
"I don't know why we accepted it or wanted to have it because it was a disaster when it was - everybody figured it would be," said Pittsburgh merchant Joe Hermanowski.
Small merchants took a heavy hit. Some downtown restaurants bought extra food, but had few diners and had to eat their losses.
On the other hand, downtown hotels made a killing. There was an immediate infusion of $10 million, plus to the local economy. Pittsburgh found itself on a world stage unlike any time since it was a steel-making behemoth during world war two.
"We've tracked since the G20 conference more than seven thousand stories written about Pittsburgh since the G20," said Bill Flanagan of Allegheny Conference. "You could probably double that worldwide."
Most of those stories highlighted the city's transformation from industrial grit to a health and financial services giant. The advertising equivalent of all that positive press, some marketers say, would've cost on the order of $100 million to buy.
At Pamela's Diner in the strip district where their specialty pancakes have won the President's taste buds, co-owner Gail Klingesmith takes the long view.
"This became the stage," she said. "For five days we had our 15 minutes. Pittsburg had its 15 minutes of fame, and it continues.
The big picture benefits of a summit don't translate for the merchant who took a financial beating, but Pittsburgh has seen an uptick in business interest, and this summer it will host two large international conventions after beating out Johannesburg and Toronto, something that arguably would not have happened without the G20 experience.