Here is a wild flower that is classified as a weed. I like it though. It is called the wild violet (Viola sp.) and grows in grassy yards. I found these growing by the sidewalk. The flower is small (maybe 2-3 cm across).
See this University of Kentucky website for more information.
The remains of a flower from last season that I found while searching for daffadils in my mother's garden to photograph. It might have been a Black Eyed Susan flower.
Here are some blue wild flowers growing along Taylorsville Road in Louisville, Kentucky. They are mixed among rocks that contain fossils from the Ordovician period (450 million years ago).
Here is all that remains of a blue-purple wild flower that was growing in the Purdue parking lot area on Charlestown Road, New Albany, Indiana. After the landscapers came in this area was planted with landscaping plants and mulch.
Here are some amazing blue wild flowers that were growing at the new Purdue building in New Albany. Unfortunately, they were wiped out by the landscapers who covered the area in mulch.
Here are some wild flowers growing in the parking lot of the new Purdue building in New Albany, Indiana. There are some nice flowers behind the building as well but too many construction people there right now to take pictures.