Though the only larval host listed at BG is not present in MN (recorded, apparently, only once in the 1880s according to Vascular Plants of Minnesota by Ownbey and Morley 1991) the HOSTS database also lists Amorpha fruticosa and Helianthus. Came to BL. I did not find an online measurement for comparison but this is quite smaller than Cycnia tenera. The wings are shiny and quite translucent.
I'm unaware of any records north of central Iowa and northwestern Illinois.
It seems too good a match to be anything else.