Joyce: Your flower appears to be a "Four O'Clock Flower". Martha Smith, U. of I. Ext. Hort. Educator, put me on the trail with the suggestion that it was Mirabilis jalapa. Mirabilis jalapa is a tropical plant and is an annual in our part of the world. However, I do believe that it is in the Four-o'clock Family (Nyctaginaceae) and there are several native Midwest species according to the Ohio State University (http://www.oardc.ohio-state.edu/weedguide/singlerecordframe2.asp?id=260).
Thank you for the beautiful picture of this flower and I am sorry that it took me so long to get an answer back to you.