Maryland's six casinos had one of their best months ever in December, generating a little over $141 million.

That's the second-best month since casino gambling began in Maryland in September 2010. WTOP-FM reported that revenue in December was up 5.7 percent from the same month a year ago.

MGM National Harbor opened in December 2016, so it's the first month for year-over-year comparisons to include all six Maryland casinos.

MGM National Harbor accounted for 40 percent of all gambling revenues at Maryland casinos, with about $57 million. That's 35 percent higher than its opening month a year earlier.

Maryland's share of gross casino revenue — approximately 40 percent — is earmarked for the Maryland Education Trust Fund, local impact grants, the state's horse racing industry and the state's general fund.