Lobelia cardinalis

This is a pink cultivar of Lobelia cardinalis L., commonly known as Cardinal flower, a native perennial of Campanulaceae (Bellflower) family. A daintier cousin of the Great Blue Lobelia, it grows from 1-6 feet tall with delicate but colorful blooms at the end of long stems.
 
For more about cardinal flower and native plants for the Midwest, especially those that do well in shade/moist areas, see the "book" on this website, Gardening with Native Plants in Shady Evanston.