Maryland is probably home to more top federal agency managers and executives, more federal agency consultants and more very-well-paid K-street lobbyists than any other part of the country. I think this would be born out if the data was arranged by zip-code and one could see the zip-codes in Maryland (and their proximity to D.C.) that have the highest incomes, that raise the Maryland statewide average. I doubt if the average income in Baltimore is a great contributor to the high statewide ranking for Maryland.
Montgomery County.