Your weekend guide to races, and horses, of interest in the mid-Atlantic region.  Parx Racing holds its biggest day of the year — and it might be the track’s biggest day ever, with Kentucky Derby/Preakness hero California Chrome and sophomore filly division leader Untapable in the house.  And that’s not all: Charles Town highlights its top filly event, the G3 Charles Town Oaks, while Delaware’s G3 Kent is the final stake of its meeting.  Here’s what’s on tap:

Among the members of the Top Midlantic-bred Poll, only one horse is in action.  Miss Behaviour, sixth on the list, is the 5-2 favorite in Saturday night’s Grade 3 Charles Town Oaks.

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