Convention centers are built to inject dollars into the local economy and attract major conventions and meetings to the cities where they are located.

From July 1993 through March 2018, the Convention Center held 7,177 events, attracted 27.2 million attendees and generated an economic impact of $13.3 billion, according to information given to the Philadelphia Business Journal by Convention Center officials.

The economic impact figure of $13.3 billion is a conservative one; it's not adjusted for inflation and it also excludes a few months.

2017 also generated millions of dollars for Philadelphia.

Much has changed since the Pennsylvania Convention Center first opened in 1993.

It underwent a $787 million expansion in 2011, increasing in size by 62 percent; and more hotels opened, including the 179-room Aloft Philadelphia Downtown, which has a direct connection to the Convention Center – like the 1,200-room Marriott Downtown Philadelphia that opened in 1995.

But not all was sunny during the Convention Center's 25-year history.

At some point large convention groups started to pull out of doing business in Philadelphia to the point where the city lost the opportunity to fill 925,000 hotel room nights and garner $1.3 billion in economic impact between 2014 through 2017, according to the Philadelphia Convention & Visitors Bureau.

Meeting planners got wind antiquated work rules at the Convention Center were costly and time-consuming for exhibitors because a third party was required to complete tasks, often for an exorbitant fee.

The Convention Center turned around in May 2014, presenting work rules that were more streamlined, transparent, cost-efficient and customer-friendly.

The new work rules were signed by four of the center's unions; two, including the Carpenters union, did not sign by a May deadline, though the group maintains it did.

They've been unable to work at the center since 2014, and their tasks dispersed among the remaining unions.

Associated troubles, once contentious and also the source of protests, has been brought to the Pennsylvania Labor Relations Board where it continues its slow process.

“There is still ongoing litigation, but the Carpenters union’s status in the building has not changed," Convention Center spokesman Pete Peterson told the Business Journal.

Both parties await the Pennsylvania Labor Relations Board hearing examiner to render an opinion.

As litigation continues, major conventions began to return to Philadelphia after the 2014 work rules were put in place, including Lightfair International, the largest annual architectural and commercial lighting trade show.

Lightfair, before its 2017 show, canceled previously scheduled meetings in Philadelphia for years 2015, 2017 and 2019 because of the pre-2014 work rules.

The group in 2015 announced its return to Philadelphia. The convention in 2017 had 23,000 attendees and 25,000 occupied hotel rooms, and it generated $27.2 million in economic impact, according to Convention Center data.

The area surrounding the Convention Center is undergoing a redevelopment that could potentially entice more convention attendees to come to Philadelphia, generating new business.

The East Market development across the street, for instance, will have outposts of Wawa, City Fitness and Iron Hill Brewery. Mom's Organic Market and AT&T have already opened there.

The former Gallery, connected to the Convention Center, will reopen as Fashion District Philadelphia, although it's development has been delayed.

John McNichol, Convention Center president and CEO, said there's also been synergy with the Reading Terminal Market, which was first acquired by the center in 1990.

The market is celebrating its 125th anniversary this year, and it continues to innovate and redevelop.