While I have never seen your isopyrum in person, the google images for it show more deeply cut lobes. I'd hazard a guess that it's more likely some species of thalictrum.

Here is a link

http://www.namethatplant.net/gallery_comparison.shtml?compare=Rue-anemone%20and%20False%20Rue-anemone

I revisited this picture while "organizing" my wildflower shots. In my travels this spring I have run into quite a few patches of Rue anemone, in various environments. When I first spotted this plant my first guess was Rue, but these were somewhat different from what I was used to seeing. These were taller(14-16") and the leaf didn't quite match. I used the above link and several other sources and yes I agree that the false rue is more deeply lobed. Usually, my first go to book is the National Audubon Society Field Guide to North American Wildflowers - Eastern Region. Their picture of Rue shows the middle lobe with a point, which corresponds to the Rue I have been seeing. This plant has a flattened middle lobe which corresponds to their pic of the false rue. I enlarged another photo of the plant and I found a more deeply lobed leaf.

Maybe thalictrum dioicum. The problem with the Audubon books is that they don't include all species. If you look at Bonap, however, it tends to include literally every species known to the regions. Look through thalictrums Bonap page and see if you can match the region to a plant.

Thanks, I will do that - eventually : )