In late summer and early fall, the Sachem (Atalopedes campestris) becomes more prominent among the active skippers. Last year it was one of the last skippers still flying in October. This one is nectaring in a patch of purple loosestrife near the river. Though the flowers are pretty, it is best not to plant this since it is invasive.
Here is a view of the uppersides of a Sachem's wings. The thick black mark on the forewing is distinctive.