Horse Gentium is my best guess as to the name of this wildflower. The plant was about 3 feet tall and this was the only bloom but there were lots of buds. I found information about it at: https://uswildflowers.com/detail.php?SName=Triosteum%20angustifolium
I actually took the photo yesterday as I walked around the campground at Black Rock Mountain State Park in Georgia.
