4/26/99- Updated 03:13 AM ET

By Mimi Hall, USA TODAY

WASHINGTON - Some of the Smithsonian museums were shut down, main thoroughfares were closed and tourists and residents were warned to stay away from downtown Washington over the weekend.

But the chaos that local officials had feared would unfold when 42 world leaders and their entourages arrived to commemorate NATO's 50th anniversary never materialized.

Instead of massive traffic jams caused by dozens of motorcades and what may have been the tightest security this city has ever seen, the streets were mostly empty over the three-day weekend - a holiday created by nervous officials who told federal workers in the immediate area to stay home Friday.

And the security concerns about holding a summit in Washington while NATO continues to drop bombs on Yugoslavia seemed unfounded as police officers languished on street corners chatting and giving directions to tourists.

Even the thousands of Serbian-American anti-war protesters who gathered across from the White House Saturday were relatively peaceful as they chanted anti-U.S. slogans and released black balloons.

All in all, it appeared as if the planning paid off and the capital city's largest-ever gathering of world leaders wrapped up Sunday with hardly a hitch.

Tourists who did venture out were astounded to see such clean, safe streets.

"It's exciting," said Burlington, Vt., restaurant executive Bill Whitby. "I'm kind of amazed at the security."

There was one security slip-up Saturday, when President Clinton briefly lost track of his "nuclear football," the briefcase that contains U.S. nuclear launch codes.

Clinton left the NATO summit so quickly as the last meeting of the day broke up that he and his motorcade left behind the military aide who carries the "football" and is supposed to be by the president's side at all times.

The aide simply walked the four blocks from the summit site back to the White House and was quickly reunited with his boss.

"We're safe," Clinton spokesman Joe Lockhart said.

After that minor mishap and a day spent defending his policy on Kosovo, the U.S. president hosted 800 NATO dignitaries and other guests under a tent on the South Lawn of the White House.

Among those who dined on grilled bison, orange and mango salad and "NATO 50th anniversary cake" were retired general Colin Powell, former secretary of State Henry Kissinger, Republican presidential hopeful Elizabeth Dole and her husband, Bob, the former senator and GOP presidential nominee.

Fancy White House fare might have been fine on Saturday night, but French President Jacques Chirac was looking for something a little less elegant when he walked into the Occidental Grille at about 5 p.m. Friday.

Passing up the blackened tuna and other stylish fare, he and members of his entourage ordered cheeseburgers, French fries and Budweisers.

Contributing: Barbara Slavin; The Associated Press