With the Washington Monument and the Lincoln Memorial as historic backdrops, the nation's capital bade a long, exuberant goodbye to the 1900s yesterday, marking both end and beginning in a multimillion-dollar New Year's Eve extravaganza of music, dance, film and fireworks.

More than 300,000 people, from Washington and its suburbs and even from around the country, sat or stood in awe as the monument counted down the final seconds with flashes of light that rose to the top of the 555-foot obelisk. The gold-and-white-colored climax followed an 18-minute collage of images by filmmaker Steven Spielberg that presented a panoramic view of America and the world.

"As we marvel at the changes of the last 100 years, we dream of what changes the next hundred and the next thousand will bring," President Clinton told the crowd. "And as powerful as our memories are, our dreams must be even stronger, for when our memories outweigh our dreams we become old, and it is the eternal destiny of America to remain forever young, always reaching beyond, always becoming as our founders pledged a more appropriate union."

Before everyone was quite ready, the president touched a sparkling torch to a fuse that rocketed, spitting and smoking, the length of the Reflecting Pool. The crowd erupted in cheers that would not cease until 2000 was many minutes old.

Then it was time for private moments. The couple from Washington kissed gently. The family from Houston broke out plastic champagne flutes and filled them with Diet Coke. The entertainers on stage began a soft rendition of "America." And people stood where they were and sang along.

"It was a very emotional experience. The fireworks were spectacular, and there was electricity in the crowd. There's nothing like being here. You can't feel this on TV," said Dona Costlow, 33, of Laurel. She was there with Bill, 35, her husband of nine years. They, too, kissed at the stroke of midnight.

As the show's opening neared, the numbers still waiting outside the lawn area swelled, causing blocks-long lines at the four public entrances where U.S. Park Police scrupulously checked bags and purses. The backup frayed tempers but, for most, didn't seem to spoil the moment.

The pedestrian delays--and some grousing over the brevity of the fireworks--seemed to be the only real headaches of the day. Throughout the city and across the region, people enjoyed a rich mosaic of song and ceremony that illustrated, in moments both small and grand, the singular occasion of this long-awaited New Year's Eve.

The District in particular reveled in the festive attention. The juxtaposed scenes of national and local celebration were fitting for a city that is both hometown community and federal capital--a city poised, its leaders fervently hope, on the cusp of a lasting renaissance in the new year.

"We thought . . . we should be right in the center of it," said Teri Johnson, 52, of Arlington.

Some of the evening revelers came well prepared for the tailgate party of the century. They brought lawn chairs, picnic baskets and blankets. As it grew dark, they switched on portable lights and read, played cards or simply snuggled. For once, they were sure, Washington would outshine even New York's Times Square on New Year's Eve.

The delays getting near the memorial were an unexpected complication, especially given the many predictions that crowds would be smaller because of weeks of State Department alerts about potential terrorist attacks abroad and at home. The security net was both high-tech and low-tech. Helicopters equipped with infrared sensors hovered overhead, scanning the crowd.

But as emcee Will Smith bounded on stage--to rousing applause led, most prominently, by the president--security was relaxed at 19th Street and Constitution Avenue NW. People sprinted through an opened section of the orange fencing to claim the few remaining viewing areas.

"It was just too many people getting into too small an area," Park Police Sgt. Frank Onolfi said.

Yet nearly 12 hours earlier, more than 5,000 people had crowded onto a short block of 12th Street NW in the morning as Clinton officially opened America's millennial weekend. "There is no better moment to reflect on our hopes and dreams and the gifts we want to leave our children," he declared, "no better opportunity to open a new chapter of progress and possibility for all people."

Just down and around the corner, the city's block party sent the mouth-watering smells of shish kebab, Indian curry and funnel cakes, the joyous sounds of salsa and the melancholy riffs of the blues drifting up and down Constitution Avenue. A steady stream of festival-goers scribbled messages about the District's future on colored squares of paper that were taped onto a "Town Hall Wall."

"What a wonderful example of the city's diversity," one proclaimed. "God bless us, everyone!"

Lisa Shattuck, 31, sat on the grass and explained why she had flown east from San Francisco, joining her mother, who traveled from Texas, and her sister, who came from Denver. "I'm pregnant and wanted to be here so I'll have something to tell my baby about," she said.

Nick and Mary Eror, who drove down from Pittsburgh nearly a week ago, also intended to be part of it all. "He wants to be in on every event," she said, motioning to her camera-clutching husband. Laughing, he quickly elaborated: "Having passed up in my youth the world fairs, I decided I couldn't wait another millennium."

The couple had walked over to the opening ceremony, not knowing tickets were required. But millennial miracle: As they stood by the barricades, someone handed them two passes. They worked their way to the front in the standing-room-only audience--close enough to get good photos. The moment was a perfect counterpoint to the previous day, which they'd spent at a museum, marveling at 10 centuries of Byzantine relics.

"You look at what [the world] was at the end of the last millennium, and here it is at the beginning of the next one," Nick Eror said. "I'm hoping to God we come to grips with what our role in the future is."

In the middle of the crowd sat a gentleman in a flowing white wig topped by a huge red-white-and-blue felt hat. Off to one side, a little boy balanced in the branches of a tree, listening intently as poet laureate Robert Pinsky offered "A Toast for 2000" and captured the meaning of the next 24 hours, "the night of cameras, dancing and champagne."

He composed just 20 lines, concluding:

The triple zeros that mark the millennial year are like three spheres

Or lights or chain-links. As the centuries pass,

Past, Present and Future, victims, villains and heroes,

Each crosses the calendar border and disappears--

Or lives in Memory, that numbers all the years.

And 100 years from now, when the copper, steel and titanium time capsule displayed in prototype yesterday is opened at last, Pinsky's words may be among the items future Americans will find. Some of the others also revealed: a copy of the 14th Amendment guaranteeing equal protection under the law, a Boston Public Library card, a sealed container of the vaccines that so greatly extended life in the 20th century, GI dog tags and the written dreams of two schoolchildren.

"I dream of stopping violence so we can live in peace," a diminutive Eric Timmons, a sixth-grader who attends the District's Burrville Elementary School, read solemnly into the microphone.

The millennial program was inside, too. In several Smithsonian Institution museums, the first of three days of programs, exhibits, demonstrations and vigorous conversation plumbed the reaches of the past to describe the potential of the future.

In the Ring Auditorium at the Hirshhorn Museum, Kent Cullers, the algorithm designer of the world's most powerful project in the search for extraterrestrial intelligence, bet 300 delighted listeners a cup of cappuccino that alien life would be contacted "not in the next millennium, but in the next 100 years."

Scientific wizards from the Massachusetts Institute of Technology dazzled with a magician's chest of inventions--a microscope that enables researchers to move strings of viruses like pieces of yarn; ultrasound projectors that can cast noise across auditoriums.

Across the dialogue spectrum, former basketball great Bill Russell held forth with current basketball stars Chamique Holdsclaw and Nikki McCray at the National Museum of Natural History. They talked about how much sports had changed over the century.

"Babe Ruth put sports on the front page, and Jackie Robinson made it all-inclusive," Russell said.

As the hours ticked down, the celebrating picked up. Many churches in the area held New Year's Eve activities for the first time, some starting at 5:30 with family worship followed by potluck suppers and concerts, even dramatic productions. First Night festivities began, from Annapolis to Leesburg, Alexandria to Gaithersburg.

There, at the Montgomery County fairgrounds, 5-year-old Samson Chang hammed it up while elementary school acrobats balanced on balls and flipped forward and back. "Bobo, stop that," his mother chided gently.

For Elizabeth and John Chang, Samson and his 8-month-old sister, Angela, represent their hopes for the new year in a new country. In 1998, they were living in a small town near Beijing. In the intervening months, John's elderly parents passed away.

"We feel they will live on through our children," Elizabeth said. "This 2000 may not mean much to Chinese back home, but to us it is kind of a new beginning."

Celebration was grabbed in small moments for the many who had to work.

At Children's Hospital, surgical care nurse Jenelle Davis was one of numerous hospital employees on duty in case of potential computer problems. Others there were pulling double shifts because of fears that something might happen on the Mall.

"Here I am without my husband at midnight for a kiss. New Year's is like my holiday," she complained, though almost good-naturedly.

Moments later, hospital administrators rounded a corner with a cart of fruit punch, cookies, turkey sandwiches and salmon canapes. Davis's face brightened. "Oh, this is nice!" she exclaimed.

As the show kicked off at the Lincoln Memorial, and no Mall fears were realized, the party truly started. Indeed, for all of the neighborhood get-togethers, all of the black-tie glamour at restaurants and hotel balls, the brilliantly illuminated Lincoln Memorial was the magnet of the night--watched by millions of television viewers thanks to CBS's nationwide broadcast.

The music blared as host Smith appeared and immediately people were dancing and cheering. "I can't hear you way back there," he told the audience, and everyone started screaming, and then, backed by a high-stomping corps of 30 men and women, Smith sang--what else?--"Will2K," a track from his newest album.

Some people expressed disappointment with the program, especially the first fireworks display, which they complained was too brief. They were confused by long silences during commercial breaks and dismayed that there was no 10-second countdown to midnight. "This was clearly a made-for-TV event," said Shauna Carsen, 28, of Washington. Others, unaware that a second, longer burst was to come, left the Mall early.

Later, problems surfaced again as the huge crowds left the grounds. Metro riders overwhelmed the nearest stations. At Farragut West, station manager Frank Biscoe estimated that 4,000 people poured into the station, and the platforms and mezzanine were jammed for about an hour. Biscoe held the crowds back by making them wait at the top of the escalator until the trains came. But dozens of riders tried to sneak to the station platform by running down the up escalators.

Metro's free shuttle bus service to carry riders from the Lincoln Memorial to the rail stations got off to a shaky start. Hundreds of buses waiting to take passengers across the river to the Pentagon and Rosslyn stations were not labeled and, in some cases, the bus drivers did not appear to know the destinations.

Still, aboard the buses, the mood was festive. Dozens of passengers wore masks, tiaras with the Year 2000, and New Year's hats. When one bus arrived in Rosslyn, passengers cheered and hollered "Happy New Year."

CAPTION: Lisa Hindman and Pat Emery, of Columbia, enjoy the music and await the fireworks and illumination of the Washington Monument at midnight.