Big-ticket musical acts including Bruno Mars, John Legend and Maroon 5 were expected to help lure 335,000 visitors to Las Vegas by nightfall - 5,000 more than last year, tourism officials said.
The holiday was seemingly custom-made to align with Sin City's boozy, bad-judgment ethos.
The Minus5 Ice Bar Mandalay Bay started handing out free champagne for hourly toasts at 11 a.m. Tourists were seen toting novelty drinks into casinos by noon.
Police planned to shut down traffic on the Las Vegas Strip at 6 p.m. PST so revelers could spill into the 4-mile stretch of road normally packed with cars. At midnight, an eight-minute fireworks display will shoot from the rooftops of seven hotel-casinos.
Law enforcement officers were keeping a close eye on the festivities.
Many hotels were dealt a full house, with occupancy approaching 100 percent and $200 rooms going for $600. New Year's Eve is typically the most profitable night of the year for casinos, and their executives worked to persuade visitors to make it a long weekend.
Many casinos offered up special "New Year's Eve Eve" events on Monday and advertised the two days before that as the biggest weekend of the year. DJs were counting down to 2014 as early as Sunday at the Mirage hotel-casino's 1OAK club.
Las Vegas was light this year on hosted nightclub bashes in which guests pay for proximity to a famous person. Original celebutante Paris Hilton was hosting one of the only such parties.
In seedier downtown Las Vegas, organizers planned a block party along the Fremont Street Experience pedestrian mall featuring Blues Traveler and Papa Roach.
New Year's Eve crowds in the city have doubled since 1990 but still lag other parties in New York City's Times Square and Copacabana beach in Rio de Janeiro.
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