General Discussion

That's owned by the Chicago Park District.

It's a public park, city-owned.

The building was renovated and the museum founded and collection is that of a non-profit, but it's a non-profit housed in a public building on public land.

No clue what right Feds would have to be on city-owned public land. But in this case, no, they weren't looking for undocumented; they were looking for assess access points for an upcoming event.