Camping at Fair Grounds?

Not around here.

Just be forwarned, during the actual fair many don't have anything or they block out "camping travelers" during the time during of the fair. I do remember running across a list somewhere, can't remember where. They are good for plan B or close in. Most are not very scenic but very handy and close to stuff. In our travels most are grass or gravel parking lot type thing. But diffently should be put on places where you could stay.

On RVParkReviews.com use the Campground Search feature and put Fairgrounds into the search box. I just got 92 results.

Cal Expo RV Park in Sacramento, California.

Almost every Fairgrounds has something for RVs. They are intended for use during events at the Fairgrounds, but.... They aren't fancy, sometimes they don't include a dump, sometimes no water, sometimes only minimal power.
Since they are "publicly" owned, the competing (commercial) campgrounds usually have convinced the Fairground agency to not advertise that they even exist.

Often if a city has a fairgrounds, then camp sites are available at them. Generally they are pretty functional, but not very aesthetic. Great place to stop for overnighting or to use as a base camp. We used the one in Santa Fe and made a good friendship with the manager.

WI has several fairgrounds that have camping facilities--Washington Cty, Sheboygan Cty, Jefferson Cty and many more.

Wayne County Fairgrounds outside Detroit. Best place to stay by far for The Henry Ford Museum, and Greenfield Village.

Does anyone publish a list of CGs at fairgrounds?

Most fairgrounds have RV parks, Just in the last month I have stayed at the Washington State Fairgrounds in Puyallup, WA and the Deschutes County Fairground in Redmond, OR. I'll also be staying at the one in Farmington, NM in a couple of weeks. Most of them will show up on the RV Park Reviews site. Some are better than others, some terrible. The one in Redmond was a gem.