I have a very old painting titled "Edes' Mill Upper Potomac" and its signed W.G. Newton. I believe this painting may have been painted bu William Giles Newton which would date this painting to the late 1800's. How can I verify that this was painted by the artist.

I'm not finding anything about it on the Internet to verify that it was painted by William Giles Newton. However, that doesn't mean that the information isn't out there on the Internet. It just may be really hard to find. I did find William Giles Newton mentioned on the following link http://www.askart.com/AskART/artists...rtist=10039353

I would suggest looking in books on artists that you might find at a public library or maybe taking it or a picture of it to an art gallery where they might have some resources for you.