Rich Archer was nervous. He'd just driven to the District from New Jersey for an important business meeting, and now, at 2 a.m., he couldn't sleep. So he did what many hungry people do when they find themselves in downtown Washington during the wee hours: He went to the McDonald's at 14th and K streets NW.

"It's familiar, it's cheap, it's safe," Archer said. "And it's open."

During the day, the McDonald's serves the standard downtown crowd: messengers, office workers and executives.

But as downtown's only almost-all-night eatery (it is closed from 4 to 6 a.m.), it's a different place after midnight. Young women in heavy makeup and miniskirts eat french fries alongside executives who have worked late at the office, and homeless people enjoy meals next to well-scrubbed suburban couples.

"It's the most unique McDonald's in the city," said James Green, an off-duty District police officer who was hired part time by McDonald's four years ago to watch over the restaurant late at night. "It's the only watering hole on the track at this time of night. People have to come here. It's a melting pot."

Added Eddie Harris, a customer who said he eats at the McDonald's every two weeks or so, "This is a place for everybody."

The restaurant is surrounded by office buildings and is near many of the city's downtown hotels. It also is near the District's prostitution strip and two doors away from a busy arcade that's open into the early morning.

The arcade supplies many of the McDonald's post-midnight patrons. About 12:30 one recent morning, an 18-year-old who said his name was Tony stood outside the arcade surveying the bustle of 14th and K streets as waves of customers went in and out of the McDonald's.

"It's good because you don't have to worry about waiting for some place to open to get something to eat," Tony said. "Look around. Look at how many people are out now. When it gets real late, that's when people like to come out."

Much of James Green's job consists of keeping the youngsters in check. One recent night, a boy who looked no older than 12 came into the restaurant three times, prompting Green to tell him, "That's the last time you come in here tonight. Don't you have school tomorrow?"

The young people, Harris said, "come in and act up, but they don't go wild. They're just loud. They don't bother anybody."

Unlike their daytime counterparts, many of the late-night customers at this McDonald's don't come in just to eat. About 1:30 one morning, a man with a serious expression studied, reading books and using a colored marker to highlight paragraphs. In a corner, two young men played chess as they ate.

"What's that, 3 to 1?" one said after defeating his opponent.

"I ain't the one keeping score," his opponent replied. "You talk so much you don't let nobody concentrate."

At a group of tables in another corner, a cluster of women wearing tight dresses chatted , sipped coffee and smoked cigarettes.

"It's a pretty wild scene," Archer said. "You have to expect that when some place is open all night in an area like this."

Throughout the restaurant, several men sat alone, some in ragged clothes, others in suits. At the counter, construction workers, middle-age couples, cabdrivers and teenagers ordered their to-go meals and left the restaurant within minutes. McDonald's workers say the late-night crowds rarely swell beyond 20 -- although the numbers tend to be higher on weekends -- and sometimes dwindle to two or three. But, they say, the restaurant never empties.

"A lot of traffic comes through here," said Leroy Jackson, 27, a grill cook. "You see all types of people in here, and some of them are different, interesting. It makes things fun."