WASHINGTON, DC. SEPT. 25, 2013: WASHINGTON, DC. SEPT. 25, 2013: Dan Nadeau, GM of the new hotel points out features to a group including Executive Chairman J.W.Marriott Jr., his daughter Debbie Marriott Harrison and her husband Ron Harrison as they view the interior atrium at "Topping Off" ceremony,( building has reached its height,) at the Marriott Marquis in Washington, DC on Sept..25, 2013 .( Photo by Jeffrey MacMillan ) (Jeffrey MacMillan/Jeffrey MacMillan)

The final beam of the Marriott Marquis Washington D.C. was lifted to the top of the 130-foot building last week in a topping-off ceremony.

As construction crews put the final touches on the 15-story hotel, Marriott executives say conference bookings for the long-anticipated convention center hotel are also coming together.

The first group of 10,000 conference-goers will arrive just three days after the Marriott Marquis Washington D.C. opens its doors in May.

The American Society of Training and Development has booked 700 of the hotel’s 1,175 rooms for its annual convention. Accommodations have also been booked at 17 nearby hotels for the three-night conference.

“We look for hotels that are in close proximity to the convention center,” said Kristen Fyfe, a spokeswoman for the organization. “This one was obviously very compelling.”

The Marriott Marquis, which will be connected to the Walter E. Washington Convention Center through an underground walkway, is expected to open May 1. The $520 million project broke ground three years ago, and officials say they are already seeing a boost in the number of conventions coming to the area.

“We are seeing a definite uptick in bookings, particularly starting in 2016,” said Greg O’Dell, president and chief executive of Events DC, which owns and markets the convention center. “This hotel will be a game-changer for us.”

Marriott would not disclose the number of conventions that have reserved rooms and meeting space at the Marquis, but a spokesman did say that “numerous groups that have never been to D.C.” had already booked meetings at the hotel.

The number of citywide conventions — defined as those with more than 2,000 room nights — has plateaued in the District in recent years, but O’Dell says that figure is already on its way up. The District expects 16 citywide conventions in 2014, up from 14 during fiscal year 2013.

The American Academy of Family Physicians is returning to the District in 2014 after a number of years — lured in large part by the completion of the Marriott Marquis.

“I can’t remember the last time we were in D.C., to tell you the truth,” said Tom Pellet, director of the organization’s meetings and conventions. “With the opening of the Marquis, returning to Washington became a lot more attractive.”

Conferences and meetings are a vital source of income for the District, bringing in upwards of $1 billion in revenue every year.

Now, as continued government budget cuts and weak economic recovery continue to take their toll on the District’s unemployment rate, which inched up to 8.7 percent in August after hitting 8.5 percent in May, officials say the convention business is more important than ever.

“Alarmingly, we are watching our unemployment levels start to go back up,” District Mayor Vincent Gray (D) said during the topping-off ceremony on Wednesday. “This [hotel] is a major step forward in that it will allow us to attract even larger numbers of people and create additional jobs.”

The new hotel is expected to create about 1,000 permanent jobs.

“It is really the missing piece of the puzzle,” said D.C. City Council member Jack Evans (D-Ward 2). “It completes the convention center.”