Ask Mr. Smarty Plants

Yes, I see that your soil is one that the USDA calls "Level, poorly drained clayey soils' - so I bet it's hard to dig up.  Good News - Rudbeckia hirta (Black-eyed susan) is a native to your area and will grow happily in moist to dry, well-drained soils.  Yes, the plants can be grown in potting soil, but better alternatives are to grow them from seed, amend your soil, or build a raised bed.

The seeds will germinate nicely if you merely scratch up your regular soil and then just scatter the seeds on the ground making sure they make good  contact with the earth.  Black-eyed Susan is so adaptable that you really don't have to do much to help it along. Many of the Black-eyed Susans found in nurseries are hybrid, bred for their showy blossoms. The Lady Bird Johnson Wildflower Center recommends that you purchase seeds from a native seed source like Native American Seed.    However, from the phrasing of your question, it sounds like you already have your plants in pots.

I would recommend that you amend your soil with some compost, before planting. That would loosen up the dirt and add nutrients to the soil.  Black-eyed Susans are a very hardy perennial. Just be sure to plant them at the same soil level that they were grown in the pot. Another solution, which helps the drainage is to build raised beds, add compost, crushed decomposed granite, and plant your Black-eyed Susan and other flowers. They will love it! 

 
Rudbeckia hirta var. pulcherrima