Could be, they have Pipevine Swallowtails there.

Here is a link that might be useful: Tiger pictures

The dark form tiger is usually in an area that also has Pipevine Swallowtails because the dark form tiger is mimicking the Pipevine. Pipevines are very noxious to birds. Matter of fact, the Black, Spicebush, Red Spotted Purple and Diana Fritillary also mimic the Pipevine Swallowtail. Dark colors on top, orange dots on the underside.

Here is a link that might be useful: Tiger Swallowtails Wisconsin

I know for sure we have PVSTs in extreme South Dane County, as I have a friend whose garden teems with GSTs, PVSTs and Tigers in the Summer months. I have never seen any other Swallowtail than BSTs and Tigers here in Madison.
I've got my eyes peeled for a return trip possibly tomorrow. In the mean time, I'm enjoying Hummers, Ladies and Red Admirals, along with the occasional Cabbage White.
I have also had regular visits with a nice Comma.

It is probably a giant swallowtail cause I saw my first today. And I'm in the twin cities.
Jacob

Sounds like a GST to me. As a kid we NEVER saw them up here in NY. Had to travel south to see them. NOW they are in our area. Same thing with Buckeyes. Mockingbirds were NEVER seen this far north - now they're commonplace! Global warming, anyone??

Exciting prospect!! I have some Rue seedlings started just for such an occasion...
I saw one fly thru about 3 seasons ago and I about dropped my tongs (I was barbecuing)!!