Just wondering if you had checked out the Yellow Wild Indigo suggestion. Here is a picture from a Duke University teacher's wildflower site. I think it looks like what you have.
Here is the link to the page:
http://www.duke.edu/~jspippen/...
Yellow Wild Indigo (Baptisia tinctoria)
Person Co., NC 13 June 2006
Showy yellow flowers blooming from spring to fall, this species is uncommon to fairly common in various dry-soils habitats across the state. It's the most common Baptisia in NC and is recognized by its small leaflets, small flowers, & small fruits. Wild Indigos are caterpillar host plants for a few butterflies including Frosted Elfin and Wild Indigo Duskywing.
