Check the Maryland Jockey Club license (WPBT934). The license lists freqs for all the tracks in MD; see the freqs for Pimlico. Appears they have eight channel radios. Pimlico is Baltimore City, according to their website.
How about aviation freqs. I wathced the blimp, foxtrot, and various other aircraft flying around all afternoon. I couldn't get over there, but I live a mile away. I also noticed a C-130 doing aircover!
I've got 451.300, 451.9875, 452.125, and 452.975 from the FCC query for the MDJC at Pimlico Racetrack. Does this jibe with what everyone else is using? The query results were a little less than specific.