If the Ulster County Fair just past is the homey small-town version of a classic American country fair, the 167-year-old Dutchess County Fair coming up at the Fairgrounds in Rhinebeck is our region’s Grandpappy of the genre: the second-largest county fair in New York State. Everything about it, from the midway to the array of agricultural exhibits spread over the 160-acre site, is huge. You could probably go for each day of its August 21 to 26 run and still not see everything. That’s probably part of the reason why 300,000 visitors are expected; a lot of people keep coming back year after year.