With the opening of the $1.4 billion MGM National Harbor casino and resort to capacity crowds, Maryland casinos generated a record $133.5 million in revenue during December, the Maryland Lottery and Gaming Control Agency reported Thursday.

The previous state casino monthly record was set in May 2016 — $104.3 million.

After opening late in the evening on Dec. 8, MGM National Harbor, the state's sixth casino, was open for 23 full days in December and recorded $41.9 million in revenue from its slot machines and table games.

Operating for the entire month, Maryland Live generated the most revenue among the state's casinos, $48 million, down 11.4 percent from December 2015. Revenue at Horseshoe Casino Baltimore increased 9.1 percent last month.

The decline at Maryland Live may reflect some siphoning off of Washington-area customers by MGM, which could leapfrog Maryland Live as the state's largest casino if it sustains the business it saw in its opening month.

But analysts said the results signal that while Maryland Live may experience short-term declines, the market likely can sustain MGM's arrival without much upheaval.

"The results were pretty much what I expected — they grew the market by about 30 percent," said Alan Woinski, president of Gaming USA Corp., which publishes industry newsletters. "The decline at Maryland Live was pretty much what it was when Horseshoe opened, below 15 percent. My guess is eventually both are going to find their niche. MGM will be more the destination resort."

Maryland Live set the monthly revenue record for a state casino — $61.8 million in March 2014 — before Horseshoe opened five months later.

Maryland Live "remains the top-grossing casino in Maryland," said its president, Robert Norton, after the latest figures were released.

The casino at Arundel Mills in Hanover announced a new charitable initiative Thursday that seemed designed to emphasize its local roots, which are central to its marketing.

Owned by the Baltimore-based Cordish Cos., the casino said it has started a program in which the first $10 wagered by a slots or table games player using their rewards card in January will be directed to the casino's philanthropic fund.

"That is a way to say to the community, 'We're here, we're local, we're not going anywhere,'" Norton said.

Horseshoe generated $29.7 million in December.

"We're very pleased with our December results, particularly in light of the new competition within the marketplace," Horseshoe general manager Erin Chamberlin said in a written statement. "As we begin 2017, we're confident we are well positioned to succeed as the business environment continues to evolve."

Horseshoe's performance came as a pleasant surprise to the Maryland Lottery and Gaming Director Gordon Medenica.

"We always anticipated the biggest impact would be on Maryland Live and Horseshoe, and for Horseshoe to have an up month was a real positive," Medenica said. He said the revenue decrease at Maryland Live "was not too severe."

Regulators had anticipated MGM's opening would create a record-breaking month, but some remixing of business was expected, he said.

MGM National Harbor, on the Potomac River in Prince George's County, attracted about 170,000 people in its first week and was at capacity almost nonstop, an MGM official said.

MGM said it was preparing a statement reacting to December's revenue figures.

Revenues also were up 6.1 percent at slots-only Ocean Downs and 1.1 percent at Rocky Gap casino and resort in Western Maryland, but fell 3.9 percent at Hollywood Casino Perryville.

The state receives a significant portion of casino revenue, which goes to support the education trust fund, the state's horse racing industry, host communities, and initiatives for small, minority- and women-owned businesses.

"Given the intense spotlight on the opening of MGM National Harbor, the December numbers for Maryland's other casinos are in line with our expectations, and we're pleased to see the increases at Ocean Downs, Rocky Gap and especially Horseshoe," Medenica said.

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