After all, it's stricter environmental regulations and clean energy policies that transformed their once "smoky city" into a beautiful place to live.
"I'm appalled that the President used my city to justify his unacceptable decision, as most other Pittsburghers are," Mayor Bill Peduto said in a statement. "My city, which has finally bounced back from decades of industrial carnage, will do all it can to promote its own environmental standards."
The Paris agreement -- an ambitious plan to combat, control and adapt to climate change -- is largely viewed as a last-ditch effort to shield Earth from the devastating effects of global warming. The accord was signed during a 2015 conference in the French capital and ratified under former President Barack Obama one year later.
Trump fulfilled a campaign promise by withdrawing the United States from the accord -- but not to residents of Pittsburgh and Allegheny County, which largely voted for his Democratic opponent, Hillary Clinton, in last year's presidential election.
In a swift rebuff, Peduto on Friday signed an executive order to further promote climate-control initiatives, committing Pittsburgh to meet a series of environmental goals by 2030, including a 50% reduction in energy consumption citywide.
'The Smoky City'
For generations, Pittsburgh was known as "Smoky City," overrun by smoke, dirt and pollution owing to a booming steel industry.
"For 150 years, this region was the epicenter of steel," said Ron Baraff, a five-decade Pittsburgher and director of historic resources at Rivers of Steel National Heritage Area, which conserves and promotes the industrial legacy of western Pennsylvania. "The thought was 'when there is smoke there's prosperity,' so no one paid attention to the fact that our environment was decimated."
Lacking regulation and enforcement, the city reached a point in the 1940s in which it was dark during all hours of the day. "Our air was so bad we had to have our street lights on 24 hours," Perduto told CNN.
In October 1948, a poisonous smog killed 26 people and impacted thousands more in Donora, a suburb of Pittsburgh, as well as neighboring communities. Sulfuric acid, nitrogen dioxide and other poisonous gases emitted by the steel industry and usually dispersed into the atmosphere were caught in foggy weather conditions and sickened the population, according to the Donora Historical Society's Smog Museum.
By the turn of the century, the industry had collapsed and Pittsburgh became a prime example of what could befall a city that did not enact and enforce strict environmental policies. It took years of legislation and action for the city to eventually reclaim its health and beauty.
"Pittsburgh is a global case study on a city that knows what it is like to be drawn down a long road of reliance on a fossil fuel industry at the expense of public health and the environment," Court Gould, executive director of the environmental group Sustainable Pittsburgh, told CNN. "Having looked at that desperate past in the face, it has done a dramatic turnaround and today is a model for prosperous economic and sustainable development."
Trump's decision to renege on the Paris agreement appears to have resurfaced painful memories of the once "smoky city." In a Tweet on Thursday, Democrat Rep. Dan Frankel said the President wanted to go back to the days when Pittsburgh was engulfed in daytime smog.
'Make Pittsburgh 1975 again'
Gould characterized Trump's comment about Pittsburgh as "laughable" and "ill informed." He believes the US retreat from the Paris agreement diminishes the country's position as a global leader.
Baraff, the director of Rivers of Steel National Heritage Area, echoed Gould's sentiment. He said the President's decision allows other countries to advance their energy industries while the US stands still.
There is no real rationale to do so, Baraff said, as the US coal and metal industries that exist today are only a fraction of what they once were. "It's positive to try and bring back jobs but it's also an illusion," he said. "Modern steel runs on a tenth of the manpower it needed before."
While Trump relies on the past to "make America great again," Baraff believes there is a "big hole" in his narrative. "The President is pretending as if somehow you can turn the clock back 40-50 years. What you can't do is make Pittsburgh 1975 again," he said, riffing off one of the President's popular catchphrases.
Environmental groups are joined by Leo Gerard, president of the United Steelworkers union, who said Trump's withdrawal from the Paris agreement "is an inexcusable blow to the US economy." Gerard condemned the President's decision to act on his campaign promise despite "the near universal support for the agreement by labor, environmental, and business leaders."
But not everyone in the region is angry.
"Ending anti-growth obstacles like the Paris agreement opens the way to a brighter future, with America in the lead," said Republican Rep. Keith Rothfus. "I stand with Western Pennsylvania manufacturers, boilermakers, power plant workers, railroad workers, truckers and miners in opposition to the Washington and global elites who want to concentrate power in their own hands."
Another Republican political supporter, Rep. Mike Kelly, referred to the agreement as "a global ideological trend" and applauded the President, calling his decision "a victory for our economy, our sovereignty, and our Constitution."
In 2010, Pittsburgh enacted legislation modeled after the federal government's Clean Air Act of 1970. Interestingly, the environmental movement that brought about the federal law was largely sparked by the writings of ecologist and Pittsburgh-area native Rachel Carson.
The Clean Air Act of 2010 transformed the city's ecology and even provided a boost to the local economy.
"The economic change that helped clear the skies was paired with corporation and government leadership in Pittsburgh," Gould said. "With sustainable business practices, Pittsburgh is a lab for metro innovation and an equitable, cleaner economic base."
Today, 13,000 Pittsburghers are employed in the renewable energy industry, and 66,000 across Pennsylvania, according to Mayor Perduto.
"Pittsburgh is the example of why the Paris agreement is good for economic development: such work is good for business, too," he said. "We've rebuilt our economy on the future and our people, not on the past."