But law enforcement officials were not relaxing Thursday, as Code Orange - the second highest level of security alert - remained in effect, with the focus now on the Rose Parade and Rose Bowl, other college football games, and numerous other holiday events and potentially tempting terrorist targets.
In Pasadena, CBS News Correspondent Sandra Hughes reports, the 115th tournament of roses went ahead under the tightest security ever seen. One thousand police officers, most of them under cover, were watching for any signs that a terrorist might target the event.
At Pasadena's Huntington Memorial Hospital, nurses and doctors were put on red alert in case of a chemical attack. Triage tents were set up outside the emergency room. The airspace over Pasadena was cleared except for military and police during the parade and game.
The tight defense in Pasadena marked the latest stage in a national effort to clamp down on security.
All week, the raising of the national terrorism alert to orange prompted cities across the country to step up police patrols, plan aerial surveillance and install equipment to detect chemical, biological or radiological contamination.
"Everything went off very well," New York Police Commissioner Ray Kelly said after the ball dropped. He called 2003 a good year: "Another year where we haven't had a terrorist attack here."
Nearly 1 million revelers rang in 2004 with the dropping of the traditional New Year's Eve ball in Times Square - a joyous, confetti-filled bash that took place under some of the tightest security ever seen.
With snipers posted on rooftops and helicopters patrolling overhead, Mayor Michael Bloomberg and guest of honor, former Iraq prisoner of war Shoshana Johnson, pressed a small globe, sending the 1,070-pound crystal ball on a 60-second drop that culminated at the stroke of midnight.
"It was brilliant," said Tanya Starkin, a 23-year-old waitress from Ireland, as fireworks lit up the sky. "Everyone was so worried about everything, and now everything is good."
In a sea of glitter and confetti outside the MGM Mirage hotel-casino on the Las Vegas Strip, sixth-grade teacher Bob Kelly cheered the new year and his newly won $1,000 from a video poker machine.
"What better way to end 2003?" asked Kelly, of Newport Beach, Calif. "I'm going to go back in there and win another one. What better way to start 2004!"
An estimated 270,000 revelers jamming the Strip and downtown's Fremont Street, watched over by about 2,600 police officers, more than 100 FBI agents and 4,000 hotel security guards, authorities said.
The festivities in Boston drew about 1.5 million visitors, reaching the same levels of the previous year. Boston's "First Night" is the oldest and largest New Year's Eve arts festival in the country.
In San Francisco, about 30,000 people gathered along the city's waterfront to watch the fireworks display against the backdrop of the Bay Bridge, which was the focus of stepped up security. Coast Guard boats trolled San Francisco Bay on the lookout for suspicious activity.
Thousands gathered in Seattle to enjoy the city's 7½-minute firework show featuring fireworks bursting from the Space Needle. More undercover officers worked the crowd than last year.
In New Orleans, an estimated 40,000 to 50,000 people watched the lowering of a giant, grinning papier mache baby in the French Quarter as helicopters patrolled the banks of Mississippi River.
Denver authorities called in off-duty officers to ensure celebrations did not get out of hand, especially at two fireworks shows on a downtown pedestrian mall, where about 160,000 people gathered. That was 50,000 more than last year's crowd, said Michael Krikorian of the Downtown Denver Partnership.
Special police units in Philadelphia patrolled neighborhoods just before midnight to look, and listen, for people ringing in the New Year by firing shots into the air. Police reported 10 to 20 such incidents, and several people were arrested on firearms violation charges. No injuries were reported.