Jefferson is huge. I went a few times 15 years ago. My in-laws lived in Madison and we would go there for weekend. My most ingrained memory was, if the people in the area needed spring rain they could count on a deluge that weekend. Glad I had a 4 wd pickup, as twice, there were cars stuck all over the parking field from small ponds and mud created after we parked.
As for demographic, it's the same with most car shows and swap meets. Same people from the era of muscle cars and we're all getting old. My local Camaro Club hosts some shows for all year and make cars and then the younger genre show up with their rice burners and twin turbo, LS cars.

I was at the Monticello IA swap meet yesterday from southern MN. My son and my dad were with and we all bought stuff. It's a decent swap meet that isn't overrun with the flea market junk that clutters up so many swap meets.
Chad

You'll get no argument from me,fairground shows will always be on my list.
Morris Il. had their annual car show/swapmeet yesterday & Sat.Weather made many stay away,but I didn't.Some good stuff showed up. :)
Also Peotone Il. annual Oil & Gas swapmeet was yesterday too,as well as the Countryside Il annual vintage Toy show.I made it there & found a nice collection of redline Hot Wheels to buy.
I wish I could've made Peotone too,but these 3 shows were too far apart from each other to attend in the same day.

I used to go to all of Gary Esse's swap meets as a buyer. Jefferson, Elkhorn, and I recall he even had one or two at Janesville. I still have friends from South Bend that make the trip several times a year to both Jefferson and Elkhorn. We would always buy spaces just to keep from having to carry everything we bought out the gate.

Me too,and Waukesha,Wis. was once on the Madison Classics list and a GREAT swapmeet/carshow.I miss that one.I found a complete NOS 1970 CD-3 windshield wiper option there once,still regret letting that go today..Some great resources are around Waukesha.

In Illinois, Santa Fe Speedway and the LaSalle Speedway (and drive in theater :hmmm:) used to be two swap meet that were my 'must go to' list. I LOVE circle car swap meets. You never know what kind of parts those guys are gonna come up with.

That was it, Waukesha, not Janesville. Thanks for jogging my memory.

It's great that there are meets still thriving! Still the best way for parts to change Hands IMO.

Charlotte AutoFair since COVID is down dramatically and I don't see reason to go back.

Locally the Cedar Rapids meet is faltering after moving from Hawkeye Downs Speedway to the fairgrounds.

I first Went to Fall Carlisle in '76 and maintained a space in the race track infield for about 25 years, just for parking. I remember "Vendor: What are you looking for? Me: '67 Chevelle parts. Vendor: Why would you want parts for that??" Memories of pre-dawn flashlights and frost on tarps. Usually came home with a full truck. Those were the days!

I used to set up at Jefferson but haven't been back for 25 years.

Some great scores at Peotone back then too!

In the Corvette world Bloomington at the fairgrounds used to be epic, but is a mere shadow of that now.

I have 2 in Phx & 1 in town next month. I always hope to find something other than a burrito but it's still fun to go & see some of my car buddies....Joe