Beauty In Black And White

This time of year, we seem to be the stopping spot for black and white moths. The north wall of the house becomes a wayside for these beautiful creatures that linger for a day or two before winging off again, and they prefer the screen of the large window. Some years we see up to 20 of these silent creatures, so far this year I have counted 4.
This photo is not monochrome, these are the actual colors of the moth. The shades of black and white intermingling and patterning are simply striking. It is a large size moth with a wingspan that can be as wide as my hand.
My limited knowledge and even more limited internet searching skills have been unable to identify this lovely creature. As far as I can tell, it is related the the sphinx variety, but the walnut sphinx usually do not appear on this side of the Rocky Mountains and my moth has dramatic white lines that enhance the subtle pattern.