Butterfly on a Yellow Wildflower

I took this picture last Saturday at the Connetquot River State Park. The butterfly is a Sulphur, but I don't know what the plant is. When I tried identifying it by examining its flowers, it seemed like it was wild parsnip. Although when I studied its leaves, I thought it could be Goldenrod (a lanceleaf variety). There are about a hundred species of Goldenrod in America. Most of them are found in the East and bloom during late summer or autumn. Knowing these facts about Goldenrod makes me think this is a good candidate for being one. But for now, I give up on trying to identify it.  I’ll just call it a pretty yellow wildflower. If you know what it is, I would love to hear from you.