Buildings rise taller than City Hall. The crumbling 85-year-old South Street Bridge begins to be replaced. And the baseball team actually wins a World Series.

Things in Philadelphia do indeed change. And in yet another sign that Center City has entered the 21st century, the old-school scrolling message system on the Peco Energy tower at 23d and Market Streets will go dark at midnight on New Year's Eve.

In its place, Peco says, a color message system with graphics and picture capability will go into operation in the summer. It will feature light-emitting diodes - LEDs - that will be 20 percent more energy-efficient.

But the purpose of the message board, known as Crown Lights, will not change, said Cathy Engel, Peco spokeswoman.

"We will continue to use the Crown Lights to salute our many civic and community organizations," she said.

From dusk to dawn since the Bicentennial date of July 4, 1976, nearly 18,000 messages in 38-foot-high white letters have wrapped around the Peco tower to let Philadelphia know about community and nonprofit events, to provide customer-service information, and to mark important moments, like the first anniversary of Sept. 11, 2001.

Its digital clock also reminded commuters on I-76 exactly how late they were for work. "That is something we will look to continue," Engel said. "People seem to like that."

After the 2,600 bulbs go out on New Year's Eve - complete with a lighted countdown to their own demise - romantics may miss the moving letters. Simple in their white glow and capitalized format, they are a throwback to a time when everything was less flashy.

"We look at our skyline, and there are things we come to expect," said Mary Grace, executive director of the antiblight group SCRUB. "And when there is a change, hopefully it will be a good one."

Grace said she hopes the new system does not become a "movie screen up there, a fade-in and fade-out, or a PowerPoint presentation."

She also questions how environmentally friendly LEDs are compared with, say, no lights at all.

"Is this really the wave of the future?" she asked. "If you want to be patted on the back for being really green, then you have to really be green."

Grace said she hoped Peco would seek community input before the new piece of skyline goes live.

Information about whether Peco needs city approval in order to proceed was not immediately available yesterday, but Alan Greenberger, executive director of the city Planning Commission, applauded the change and is glad Peco did not just shut down the system.

"It has been a great message board in the city for so many years, I wouldn't want to lose it," he said. "Probably for about a half-hour there will be a sense of loss. Then it will be over."

Greenberger said that as people become more conscious about saving energy, buildings are no longer lighted up as they once were and cities are getting darker.

"So to have something that is fundamentally about light, and to have Peco the first one to do it and change it to an energy-efficient system, is a great way to keep the city lit," he said.

The change is part of a range of projects costing $15 million to make Peco more energy-efficient. Peco did not provide the specific cost of the new lighting system.

The Philadelphia skyline once lagged behind other cities' because of the Gentlemen's Agreement that forbade buildings to be taller than the hat of William Penn atop City Hall. But it has undergone a range of changes over the last several years.

The Cira Centre in West Philadelphia can put on a veritable light show on its facade, and the Comcast Center has a look so modern it has been likened to a USB memory stick.

In 2005, Boathouse Row caused a minor stir when it switched over to color LED lights.

Not convinced that change has come? The Peco tower is particularly visible from the South Street Bridge.

Appropriately, the bridge closed for two years this month to make way for a more modern span.