What state are you in? His face doesn't strike me as someone familiar, but the clothing and hair definitely suggest 19th century American. The reason why your state may be relevant is that it could be someone who was prominent locally. (And also possibly not - but it would be one way to narrow the choices.)

If this thread proves unsuccessful, I would recommend contacting local libraries and (if there are any nearby) historical societies and college-affiliated art museums. Take a higher quality photo first, however.

Also, is there any evidence of an artist's signature on the painting? If so, that would be another possible clue. If a signature is available, post it here as well.