MGM National Harbor, other casinos report record revenue Associated Press · January 5, 2017 at 8:21 pm BALTIMORE (AP) – State gaming officials say the opening of MGM National Harbor helped Maryland’s six casinos bring in record revenue. Maryland Lottery and Gaming said in a news release Thursday that MGM in Prince George’s County generated nearly $42 million from slot machines and table games. The casino opened on Dec. 8. Officials say that amount and the revenue the other five casinos generated in December brings the total to more than $133 million. The previous revenue record of more than $104 million was set in May 2016. Copyright 2017 The Associated Press.