It's fair time and we have 2 County Ag Societies that we usually end up filing a bunch of CTRs for.

Would a entity of the County be a department or agency of the U.S., any State, or any political subdivision of any State?

Initially I thought so but now I'm second-guessing myself...

We have the same situation and we have always included them in our CTR filing. They have a different EIN then all of the other county related accounts, so we don't exempt them. Maybe they should be? No one has ever said anything regarding this.

Any ideas on what type of document(s) I would need to prove that they are a govt entity?

Best guess is that they are not actually part of the county's organization structure. They may receive county support, but you probably can't call them part of county government.

As John said, I don't think they are. If they were associated with the county, they most likely would have the same EIN.

What is an Ag Society?

Just talked to FinCen and they told me that I could exempt the County Ag Societies as they are entities acting with government authority.

Hmmm. That kind of surprises me. I'd keep a record of whom you spoke to at FinCEN if I were you. I googled "County Ag Society" and came up with a lot of websites. Most suggested that the primary business of these groups is to promote agriculture within the county and to put on the annual county fair/rodeo. I even found the Burnett (WI) County Ag Society, way up in northern Wisconsin. Now THAT was a surprise!

I agree with John. I would be looking for a direct link to the county government and make sure that they are not really a 501(c)(3) type organization.