Nice photo, Joanne, and a very good question about recognition details or field marks to consider. You have already recognized that it is a Geometer by those widely spread wings and overall size [ruling out Pyralids (too big) and all but a very few Noctuids (wingspreading)]. For me the next key feature is the shape of the hindwings, here rather pointy or "angled," not smoothly rounded. This ought to immediately make us think of the group known as the Angles of the large genus Macaria (formerly Semiothisa). There are some other angle-winged Geometrids but, usually, the coloration of them is different from that of the Macaria Angles.

Now we have to compare the fine details in the photo with examples of named specimens - dots, lines, blotches, overall coloration, etc. In this case we can immediately dismiss most of the Angles because they are not as heavily mottled as your species. If you scroll through the MPG Living Moth Plate 32a [happily, first plate in the Geometridae] you should pretty easily locate the species. A photo there by Larry Line is almost a perfect match for your photo.

It gets a little easier with time and experience. I wish I could say it becomes really easy or simple. It doesn't. There are just too many moths and too much variation, and puzzles abound.

This excellent photo appears to be a first of species for the Guide here and is thus a nice contribution to the collective effort of building a moth identification database. Thanks for making the contribution.