Back when this poll was started, my choice was easy. It would have been the Northampton (3-County) Fair in Massachusetts, which sadly stopped racing after 2005.
My most favorite today would be the 4-day mid-July race meet in Prineville, Oregon, aka The Crooked River Roundup. I suspect less than 5 PaceAdvantage members have ever been there.
A close second would be the Timonium Fair which runs late August thru Labor Day Monday. (Word has it that if these covid gathering restrictions ever end, Timonium will be adding an additional 3 days to their current 7-day meet.).
Honorable mention would go to Kentucky Downs, which has a very unique track layout, huge field sizes, and betting handles.
If I was forced to limit myself to the specifically named tracks, my choice would be Monmouth Park.