Wildflowers should be planted in the same habitat where they naturally grow. Jacks, Dutchman's breeches and wild phlox naturally grow in moist, rich, humusy forest soil under broadleaved deciduous trees that allow lots of sun in the early spring and fall and provide dense shade in summer. They will not thrive and will likely die in dry, sandy soil in year round shade.

Coneflowers come in many types, some like dry soil, some like moist, some can tolerate light shade. They are all native to the prairie which provides deep soil and little shade. They will fare worse than the woodlanders in the dense shade of a pine forest.

there are plants adapted to all conditions, but you will find few showy flowering plants that like to grow in dense shade. Take a walk through natural pine forests in your area in all seasons and observe what plants are growing. These are the plants that you can consider for your woods.

Check the link below for the Illinois Native Plant Society and see if there is a chapter near you. Their members will be able to help you find suitable plants.

Here is a link that might be useful: Illinois native plants

I don't have experience with your soil I am envious! I have heavy clay. and too much sun and I believe naturally acidic just because of where I live. I never had it tested. But if I were you I would try to obtain a wood lily because that's their ideal. I bought 8 this year and although three survived only one bloomed. I was told it's the flower of the canadian state of saskawetchen so you might be able to purchase one thru them good luck Sorry I can't be more helpful I'm sure someone else will. Sarah

Here is a site that lists some of what is found in sand prairies in your state.

Vera

Here is a link that might be useful: Illinois Wildflowers

Grove sandwort grows farther west of you in pine woodlands of the rockies, small white flowers. Harebell migt grow for you.

Prince's Pine (Chimaphila umbellata)has tiny delightfull flowers that are quite a impact when seem en masse. Its in the faimly of wintergeens so its pretty inconspicuous because of its size. A tiny treat, especially if one has a magnifying glass!

Here is a link that might be useful: Prince's Pine

WOW This is the first time I've posted and you folks are AWESOME. Thank you very much. I haven't had time to check out the sites, but rest assured I will.
Thanks again, Snitch

Is there dampness under the sand?
I have damp sand and Linnaeus borealis, trientalis, clintonia borealis, cypripedium (3 kinds), a beach lobelia, gentians, ladies' tresses, and so on!