Do You Recognize This Person?

This is a detail from a lesser-known portrait of a better-known figure from Revolutionary history. In fact, this individual is one of the most easily recognized people in all of American history—but our image of the person comes from a different point in life. Can you guess who it is?

The full portrait and name of the subject appear here.

The original painting is in the collection of Harvard University, a donation from Dr. John Collins Warren. [Ooh, is that a clue?]