This is the third year I've purchased and planted an Oklahoma native Giant Coneflower, Rudbeckia Maxima. I love them. They grow to 6 feet tall and have huge flowers.
The leaves are a bluish grey which is also a favorite of mine.
The University of Oklahoma has a database of Oklahoma native plants and it says that this beauty if native to Choctaw county.
The Lady Bird Johnson Wildflower Center in Austin calls it a Giant Brown Eyed Susan. Their horticulturist says it is found in moist open spaces from East Texas to the East Cross Timbers.
I'm going to try watering it more and see if this one takes hold and returns next year.