Skippers are hard to identify. With a little bit of help from my friends, I labeled this one as a Least Skipper. Field marks include its small size, rounded wings, and dark forewings. The checkered antennae also help.
The Least Skipper inhabits the eastern United States and southern Canada. This butterfly is often abundant, but the flight can be short-lived. Least Skippers fly about damp, tall grasses along roadsides, streams, and meadows. I found it in unmowed grass along a small creek at the Dennison, Minnesota, sewage treatment ponds.