When President Donald Trump withdrew in June from the Paris Agreement on climate change, saying, "I was elected to represent the citizens of Pittsburgh, not Paris", it went over like a lead balloon in America's steel city.

Pittsburgh Mayor Bill Peduto tweeted: "Fact: Hillary Clinton received 80 per cent of the vote in Pittsburgh."

But politics aside, eyes rolled at the implicit equation of Pittsburgh with Mr Trump's Rust Belt power base.

Today's Pittsburgh is nothing like the Rust Belt cliche. In fact, a few Rust Belt cities have begun recovering - and Pittsburgh is showing the way.

The city has reinvented itself, grafting the new onto the old. Gleaming high-rises soar above old red stone towers, new condos and cafes sprout among vacant lots and between the shells of abandoned factories; this summer alone, 21 new restaurants are slated to open. Uber's driverless cars are a common sight, their rooftop cameras spinning as they are tested on the city's streets. And in a country of largely mediocre airports, Pittsburgh's is rated one of the best in the world.

METAMORPHOSIS

The famed city of oil, coal and steel, once one of the richest in the world, crashed in the early 1980s.

"We had unemployment rates in double digits, we had food lines; it was unparalleled," says Ms Melanie Harrington, president and CEO of the non-profit economic development organisation Vibrant Pittsburgh. "People were leaving because there were no jobs."

But underpinned by top universities and research institutions, old-money philanthropic foundations, plus political leadership and a sense of community, the city of just over 300,000 has reinvented itself to become a research, technology and arts hub.

The recovery began some 20 years ago, and gained momentum in recent years.

"I think traditionally people have maybe discounted Pittsburgh," says Mr Brendan Quay, co-founder of HiberSense, a climate control technology start-up working out of the buzzing office spaces of Alphalab Gear, a start-up accelerator.

"But nowadays, Google and Facebook have moved in. Oculus is here, Uber is here, Ford has put in money for driverless cars, so we have the tech giants and we have talent from the universities and colleges.

"Now, more and more people are seeing it as the place to be, a place that can compete with New York or Silicon Valley," Mr Quay, a 24-year-old computer engineer from the University of Pittsburgh, tells The Straits Times.

Evidence of the city's reinvention is sometimes hidden in plain sight.

Sandwiched between disused warehouses and the Allegheny River, a 120-year-old building that in the 1950s produced steel pipes for the world's first nuclear-powered submarine, now houses the Carnegie Mellon University (CMU) National Robotics Engineering Centre (NREC), which creates robotics technology - from driverless vehicles to a 3D painting system in use for F16 fighter jets.

Located inside the high walls of an old steel stamping factory is a company called Astrobotic, which has a real-size model of a lunar landing craft sitting in a cavernous workshop.

In 2019, a working version of the lunar landing craft will take 265kg of packages to the moon. The bulk of it will be scientific instruments but, individuals, for a fee starting from US$460 (S$630), can send tiny packets to the moon. The company has received several, including one of fingernails and hair to preserve the client's family DNA on the moon.

In another district, a former cookie bakery now houses research facilities for Google and the University of Pittsburgh's Human Engineering Research Laboratories, which develops sophisticated electronic wheelchairs. Demand for them is growing as an ageing population remains active while also suffering from disabling conditions like diabetes.

Since a dip in 2008 to 2009, per-capita growth in the Pittsburgh area in productivity, average annual wage and standard of living has outperformed the national average. In 2014, the city's gross domestic product increased by 4.5 per cent, ahead of the national average of 4 per cent for metropolitan areas.

Growth has been somewhat uneven, and there are still blighted neighbourhoods as in many other American cities. But from 2010 to 2015, overall employment grew by 4.3 per cent, and relative poverty declined. Ageing remains an issue although a once-precipitous decline in the city's population has slowed.

"Pittsburgh was a leader in bottoming out as it were," Ms Audrey Russo, president and CEO of the Pittsburgh Technology Council, a tech industry association with over 1,300 members, tells The Straits Times.

"Then a significant but loosely affiliated leadership that represented CMU, advanced manufacturing, and some of the research that came out of the University of Pittsburgh Medical Centre began to weave themselves together.

"The other variable was philanthropy; Pittsburgh has the second-highest pool of philanthropic money in the US. It plugged a huge hole and invested in the arts, in education, in some of the neighbourhoods," she says.

The multiplier effect of the synergy between universities and the private sector is evident. One of the co-founders of HiberSense is the former chair of computer science at the University of Pittsburgh, Professor Daniel Mosse. The NREC spins off companies to commercialise its technology; Astrobotic is one such spin-off.

PEOPLE PROBLEM

However, the NREC is concerned about human resources, says its director, Dr Herman Herman.

There is a shortage not just of engineers but also of technicians, says the Indonesia-born Dr Herman, who is in his 40s.

He came to Pittburgh in 1986 and got his PhD in robotics from CMU.

"We're trying to educate more engineers and technicians because there are plenty of positions. Some of these skill sets don't require a PhD."

He adds: "Robotics, if you take related industries, already employs easily tens of thousands. Like today's auto industry, robotics will employ millions. Think of it - you will need support to service the robot you have in your house."

"This is about the evolution of technology. People have to catch up with it."

President Trump's promises that the glory days of coal and steel will return to Pittsburgh do not find much traction in the steel city today.

"If you ask students, 'Do you want to work in wind turbines, photovoltaics, power electronics systems, or do you want to work in coal?', what do you think they will go for?" asks Dr Brandon Grainger, a power conversion engineer and research assistant professor at the University of Pittsburgh's Swanson School of Engineering.

It is almost a rhetorical question.

"They want to work on the cutting edge, the new stuff. It's more fun."