Thank you! I've researched your suggestion and it sounds like a match!

Thanks very much all. I googled it (images) and senna pendula is spot on. It also travels under the name cassia pendula with common names Easter cassia (in south) and Christmas cassia (in north). The speed with which plants are identified on this site is a credit to the skill of the members. Thanks again, John

Nonmember, thanks for the suggestion. I then looked up various species of Helianthemum, and I found this one that seems to fit: Helianthemum corymbosum (Pine barren rock rose) Here is a link that might be useful: Pine barren rock rose

I don't profess to know my plants but is this a wetland situation? it looks to me like it could be purple loosestrife which is invasive in the Midwest.