The Metro subway system, built in the 1970s to ferry federal bureaucrats to work, will stay open past midnight on weekends starting in November in an experiment being celebrated by many as part of Washington's transformation from a button-down town to a vibrant city.

"This is an indication that the city is growing out of its prolonged adolescence and into maturity," said Dorn McGrath Jr., a professor of urban and regional planning at George Washington University.

"It's no longer a 100 percent federal government-dominated town," said Alfred Robinson, 32, a research assistant from Arlington, who rode the Red Line at midnight Saturday to see friends in Dupont Circle. "There's the high-technology growth in Northern Virginia. . . . Downtown Washington is going through this huge revitalization, with MCI coming in and Adams-Morgan becoming popular for nightlife. There's more than ever existed 20 years ago."

Metro's board of directors voted unanimously yesterday to extend the subway's closing time on Fridays and Saturdays from midnight to 1 a.m. for an eight-month experiment starting Nov. 5. After six months, the directors said, they will evaluate ridership figures and the impact on daily service and consider extending the closing time to 2 a.m.

The last time Metro's evening hours were extended was in 1978, when the system moved its closing from 8 p.m. to midnight.

"This has been a long time coming," said Jim Graham, a Metro board member and main proponent for extended hours.

Graham, who represents the restaurant and bar neighborhoods of Adams-Morgan and U Street NW as a Ward 1 Democrat on the D.C. Council, came into yesterday's board meeting with four boxes filled with 16,000 signatures on a petition supporting later subway hours.

Running trains until 1 a.m. will generate 4,600 new trips each weekend night, according to Metro.

In addition to revelers on the town, the new service is likely to attract late-night workers such as Victor Harden, 39, a housekeeping manager at the Grand Hyatt who must leave work 10 minutes early to catch the last train at midnight on weekends. "Staying open till 1 a.m. is going to help me a lot," Harden said.

Many of the 50,000 people who work in hotels and restaurants in the Washington region rely on transit, said Eric C. Peterson, president of the Restaurant Association of Metropolitan Washington, which has been lobbying for a 2 a.m. closing. "This is a step in the right direction," he said.

The campaign to extend Metro service attracted unlikely allies that included businesses and environmentalists, Mothers Against Drunk Driving and rock radio listeners. Clubgoers in Adams-Morgan and the U Street area joined forces with elected leaders in the District and Montgomery and Prince George's counties. "I've gotten more calls and letters about this than almost any other issue we've handled," said Gladys W. Mack, vice president of the Metro board.

For years, Washington has had the earliest closing time of the nation's largest transit systems, drawing complaints from locals and visitors. "People have asked me, what kind of a rinky-dink town is this that the subway shuts at midnight?" said Chris Zimmerman (D), an Arlington County Board member and representative to the Metro board.

The complaint became so common that it made its way onto a silkscreen and greeting card created by Alexandria artist Clay Huffman in 1986. The design shows Cinderella abandoning her carriage on a Metro subway platform and running for the closing doors of the last midnight train headed for Silver Spring.

Yesterday's vote came after a week of negotiations between those Metro board members opposed to longer hours and those pushing for an immediate extension to 2 a.m.

John Davey, the Prince George's representative to the board, was the most vocal critic of the plan. He worried that extending the hours of the system would reduce the "maintenance window" -- the early morning hours when the trains stop running and tracks can be shut down. That's when crews use heavy equipment on the rails to fix existing problems and try to prevent new ones.

Metro General Manager Richard A. White told board members that Metro could handle service as late as 2 a.m. but that any later service would strain the limits of the current maintenance system.

Extending closing until 1 a.m. will require Metro to do the same amount of maintenance in a shorter period of time by hiring 18 more workers and buying two pieces of major equipment.

Because fare-box revenue doesn't cover the cost of service, the three jurisdictions that help subsidize Metro -- Maryland, Virginia and the District -- would have to pay a combined $1.5 million a year to cover the expense of running weekend trains until 1 a.m. They would also have to pay a one-time capital cost of $1.1 million.