"Best ride" kind of depends. Some of the smaller one-day rides can be very nice, not so crowded, and fun. The big rides with thousands of riders are good too. And then there are the challenge rides, the "brutal", "horrible", etc rides.
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I don't know of any comprehensive list. When I see a ride report or a mention of a ride that sounds interesting, I'll save a link into my "next year" bookmarks.
google "(state) bicycle events" can usually help. For instance:
Kentucky bicycle events doesn't come up with a state list, but the big clubs do show, and they have yearly rides.
Kentucky bicycle 100 mile ride worked even better. The 100 mile events usually have shorter distances too.
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Old Kentucky Home ride in September from Louisville is popular.
The
Horsey Hundred in the Bluegrass area at the end of May was great, well organized, and scenic.