Members of an industrial panel had numbers to back up the fallacy that industrial activity left the city along with the major manufacturing outfits that closed decades ago. About 104,000 people, or one fifth of Philadelphia's population, are employed by an industrial business, creating $323 million in annual tax revenue. Additionally, city officials expect 2,422 acres of industrial development to take place in the city over the next 20 years.

"We're not a post-industrial city any more," said Prema Katari Gupta, real estate director of the Philadelphia Industrial Development Corp. "The industrial sector is still a vibrant part of the city's economy."

Granted, things have changed since the days of major active smokestacks, and it's not as though vacant industrial buildings aren't part of the city's reality. There are 1,288 acres of vacant land and buildings in the city that are zoned industrial, said Scott Page, founder of urban design firm Interface Studio.

"We have all of these industrial sites that have been laying fallow," said Christopher Terlizzi, chairman of ULI Philadelphia, in a GlobeSt.com interview. "They're fertile ground for repositioning and reuse."

But there are also industrial buildings that are perceived as being vacant by community members that are actually in partial use by small manufacturers, Page said. The challenge is finding ways to incorporate those businesses into other parts of the city into a mixed-use environment and rezoning and reusing large tracts of vacant industrial space.

"We have a lot of small industry, and they're valuable for the city," Page said. "These are the types of things we want to retain."

Some ideas for repurposing a blighted industrial site include conversions into charter schools, markets and art spaces.

On the other hand, many companies with an industrial component would love to enter the city, said Michael Cooper, and assistant vice president of the Philadelphia Industrial Development Corp. "Companies want to be in the city because people are close and want jobs," he said.

The problem is that land costs within the city are many times more than what industrial companies currently pay in the outlaying areas they currently inhabit.