It's not like it used to be. Dozens of traders, brokers, and market-makers descend to the basement trading floor of the old

Philadelphia Stock Exchange

at 1900 Market St. every working day, down from the many hundreds that shouted orders in the 1980s and '90s.

At least they have cooler gear these days.

PHLX, founded in 1790, was sold to the global Nasdaq OMX Group Inc. by members and investors for $652 million in 2007, as high-speed trading was turning even the frantic New York Stock Exchange floor into a quiet retreat for aging professionals.

It was long one of the city's most important business incubators. Its members built companies such as Susquehanna International Group, now based on City Avenue, whose 1,600 traders and support staff move markets worldwide, as well as dozens of smaller investment firms. Nasdaq OMX PHLX traders also supported local businesses and institutions, from pizza joints and chain bars like the now-closed Elephant & Castle on 19th Street, to Main Line country clubs.

Nasdaq's options business, centered in Philadelphia, is now the nation's largest options-trading group, according to Options Clearing Corp. data. Nasdaq's electronic stock-trading business also has operations here. The group's data center is in North Jersey.

Local firms such as Dan Bigelow's Monadnock Capital Management and Tim Lobach and Steve Cheseldine's Keystone Trading Partners still trade on the floor. So do outposts of Chicago and New York firms.

Firms that have remained in this business typically have invested in new trading systems that allow a trader to follow dozens or hundreds of securities at a time, up from a handful in the old days.

"We trade 1,100 issues" on the Nasdaq Philadelphia floor and the rival, all-electronic BATS exchange, Lobach told me. "There's still a benefit to the open outcry [by live traders] in filling orders that need more complexity." His firm employs two traders on Nasdaq's Philadelphia floor, and others at remote or "upstairs" locations.

Two floors up, staffers report daily to rows of terminals in Nasdaq's operations center. The market remains a self-regulatory organization and follows Securities and Exchange Commission rules. Its website lists dozens of payments since the merger for alleged rule violations; at least two settlements topped $1 million.

Philadelphia veterans are now prominent in Nasdaq's leadership.

Tom Wittman, former PHLX software development chief, is Nasdaq's executive vice president for global transaction services. Frank Hatheway, a onetime PHLX currency trader, is now chief economist for Nasdaq OMX. Barry Nobel, John Egan Jr., and Kevin Kennedy are among the former PHLX traders who are now managers at the operations center. Ex-PHLX Chairman Meyer "Sandy" Frucher is Nasdaq's vice chairman.

"No other workplace like it," says Marc Eisen, a former trader who is now vice president at Chaikin Analytics in Philadelphia, which sells market data and guidance to pros and investors via iPad and desktop applications.

"The traders were everyone from blue-collar guys from Southwest and Northeast Philly right out of high school, to guys like me from middle-class backgrounds, to MBA grads," Eisen added.

"You had to have thick skin to be a trader. But it was also a very tight-knit family. You could have a screaming match with a broker, and then go grab a beer after the close."