Trevor, I'd suggest you email Hanover and ask them, their website may not be up to date but they obviously know where to find the data! Are you familiar with the book "The X Factor" by Marianna Haun? It is an interesting concept but not without critisicm and more then a few skeptics. Yes I was at Teeny Lodge earlier in the week, I think I'm in the good books this time, no bad news and I remembered the cake!
As another thought you could just email the UStrotting site direct, I found them very helpful in the past when I asked them how many mile tracks there are in the US, they sent me the whole track directory! Only 16 mile tracks and around 800 half and five furlong ones when you count both pari mutueal and fair grounds in the country!