I found this clearwing moth last August in the wild flowers at the St Croix Scenic Riverway's Marshland Visitors Center. At first I thought that it might be a nessus sphinx moth, which is similar and which I have seen in Minnesota in the past, but when I took a closer look I noticed that it did not have many scales on its wings which would make it a clearwing moth.
There are numerous different types of clearwings. My guess is that this is a slender clearwing. The wings, front and back, of the clearwing moths are hooked together with numerous curved spines. This is different then other moths, who have wings that are not attached to each other, and similar to wasps, which these moths often look like. This is a natural form of defense for these moths, which are often called wasp moths.