The Washington Post was given an exclusive tour of the new MGM National Harbor before its grand opening on Dec. 8. (Ashleigh Joplin/The Washington Post)

As guests slurped oysters, sipped cocktails and sought glimpses of VIPs ranging from U.S. senators to Miss World, one man checking out the new MGM National Harbor casino and resort shouted what many in attendance were thinking: “$1.4 billion looks good!”

The glitzy new entertainment destination opened Thursday, marking what officials hope will be the beginning of a new era of economic growth and prosperity for Prince George’s County.

The casino is also a point of progress and pride for county residents who have long complained of being snubbed by high-end retailers offering the type of amenities and cachet that the resort brings.

“This facility is a watershed moment for us,” County Executive Rushern L. Baker III (D) said Thursday as he and other top elected officials gathered to mark the opening. “The comments I made when I first took office — about how we are the economic engine of Maryland — and I dare say the Washington region — this facility says that is true, and it also says to businesses ‘This is the place to come.’ ”

Maryland Gov. Larry Hogan (R) called the resort “simply amazing.”

“MGM National Harbor will have a transformational impact on this region,” Hogan said. “It will be a tremendous economic benefit to Prince George’s County and the state of Maryland.”

In addition to the nearly 4,000 jobs created, the $1.4 billion casino resort is projected to generate between $40 million and $45 million a year in tax revenue for the county — and millions more for the state.

As dignitaries and special guests entered the resort for an opening ceremony, they lauded its offerings of fine dining and an intimate concert venue in addition to the gambling. They chuckled at promotions saying that “Mankind was not born to be bored” and that MGM is in “the holy s--- business.”

When the doors opened to the public at 10:30 p.m., a half-hour earlier than scheduled because of the crowds and the cold, hordes of would-be gamblers rushed inside. By 11:30, the casino had reached capacity — about 9,000 — and officials were not allowing any more patrons in.

The elevators from the parking garage were so packed that guests feared they would overload, and they shouted “Nooo” at those who tried to shove their way in.

Security officers tried to ask people crammed into a vestibule to go back outside, and many refused, pressing up against the glass doors instead. “Open! Open! Open!” they chanted, and “Let us in! Let us in!”

Maryland State Police temporarily closed two Capital Beltway exits leading to National Harbor in an attempt to unjam the Woodrow Wilson Bridge, which was clogged with traffic from Northern Virginia at 11:30 p.m.

Inside, nearly every machine in the 125,000-square-foot casino was taken almost as soon as the doors opened. Roxana Pimental, who had waited outside for two hours, seized a Mayan wheel game. “The wait was so worth it,” said Pimental, 31. “I want to play all of them. All of them.”

Others groused about not being able to find an open slot machine as they lined up in ever-growing queues at the many casual eateries. Around 12:30 a.m., security reopened the doors and a new crowd swarmed the lobby and conservatory.

Domingo Bernardo, a 46-year-old construction worker and salesman from Fort Washington, was eager to get right to the Texas hold’em tables. “It’s gonna be more fun tonight because a lot of dealers are rookies,” said Bernardo as he waited outside before the casino opened. “Sometimes they make mistakes, but you make money.”

Claude Thompson, 68, of Bel Air, Md., had the same hunch. “Some people think the machines pay you better to get you something” on opening day, the former UPS driver said.

Thompson misunderstood and thought the casino opened at 11 a.m., so he had arrived at 8 a.m. After waiting 14 hours, he was even more eager than most to get inside.

Brandy Seipel gave him a run for his money, though. The 33-year-old insurance agent from District Heights, Md., live-streamed her reactions for about 30 friends watching on Facebook Live. “It’s so beautiful,” she squealed, spinning around on the steps of chef Marcus Samuelsson’s new restaurant. “You gotta come. Even if you have to get up for work at 5:30 a.m. I’m going to pull an all-nighter here. I’m going to.”

The casino, nine miles south of the U.S. Capitol, sits on a 23-acre parcel on the banks of the Potomac River. Maryland officials, marking the opening, noted the building’s architecture as a gateway landmark just off the Capital Beltway.

But MGM aimed for the glamour of Las Vegas and Hollywood.

Actress Sarah Jessica Parker and the celebrity chefs José Andrés, Bryan and Michael Voltaggio, and Samuelsson, who have restaurants in the resort, posed for selfies as politicians and corporate officials mingled during the open house earlier in the day.

Parker chose the casino as the site for her first stand-alone boutique. During the pre-opening hours for VIPs, she knelt to personally help a shopper try on a pair of $350 Italian-made shoes, while a line of curious customers grew longer by the minute.

The resort has already booked Bruno Mars, Cher, Sting and Ricky Martin for concerts in its 3,000-seat theater, which will also feature comedy shows and boxing matches.

Also at the resort is a day spa and a large collection of art by local and international artists.

Then there’s the gambling: The casino will be open 24 hours a day and has more than 3,300 slot machines, 124 gaming tables and 39 poker tables.

The sixth casino to open in the state — and the first in the greater Washington region — MGM National Harbor opens after winning a long and expensive campaign to expand gambling in Maryland. he Maryland Lottery and Gaming Control Agency selected the company out of three bidders for the state’s final casino license three years ago.

With five other casinos in Maryland and many more along the East Coast, some industry analysts have questioned whether the market is saturated. Others say there is still room for growth in a state where casinos have yet to reach their revenue projections.

“Is gaming vibrant enough to take some more? Yes,” said Richard Clinch, who tracks the gambling industry as director of economic development at the University of Baltimore’s Jacob France Institute. “I think MGM creates a market because it is a national-level operator. It is one of the elite operators of casinos.”

That’s why, officials say, MGM could be a driving force in attracting international visitors. Although the casino is expected to attract gamblers from across the Washington region, MGM executives say their goal is to draw people from across the continental U.S. and worldwide.

Still, MGM is likely to affect revenue at Maryland Live in Anne Arundel County, its nearest competitor, and one that markets to the District and Northern Virginia, where casino-style gambling remains illegal.

The opening was a major undertaking for local law enforcement. Police deployed dozens of officers to manage traffic near the casino, which residents and commuters fear will exacerbate gridlock in the area. Fences were put up to discourage pedestrians from crossing outside the crosswalks, and the county police helicopter started patrolling the skies in the early afternoon.

Traffic backed up bumper to bumper before 7 p.m. on MGM National Avenue and didn’t let up. Police officers directed traffic to the casino, but it moved slowly.

The police command center at National Harbor remained a hive of activity throughout the night. At about 11:20 p.m., police tweeted that the casino parking garage — with 5,000 spaces — was at capacity and shut down the entrances.

Traffic on roads leading to the casino ground to a halt, and police said there was a massive backup on the Woodrow Wilson Bridge leading from Northern Virginia to National Harbor.

Officials expect more traffic in the area into the weekend.

Outside the casino, some who gathered around weak heat lamps to await the opening gave in to the bitter cold and went home. Henry Rubio, 24, of Alexandria tuckered out around 7:30 p.m. “It’s way too cold,” he said through a ski mask. “My toes are freezing.” Because of the traffic, he and his friends trekked half a mile to a McDonald’s down the road to catch a ride.

But inside the casino, the VIPs were reveling already. Zeno St. Cyr III, a Prince George’s County activist, said he was most excited about the amenities, which is what many resident were approving when they voted to bring the casino to Prince George’s in November 2012.

“That’s what we are getting,” he said. “I know my wife would like to go to the day spa there and get pampered. I have no idea how much it’s going to cost me!”

He’s not much of a gambler, he said. But he played $50 at the slot machines on Thursday night and managed to win $222. Cashout voucher in hand, he looked around the gaming room and said, “It’s really something special.”

Bill Boasberg, general manager of MGM National Harbor, said the building, the size of five city blocks, is the product of thousands of workers.

“After we christen our resort with an inaugural party tonight, we will open the doors to the public. And then they will never close,” he said.

Lynh Bui, Arelis Hernandez and Faiz Siddiqui contributed to this report.