Tradescantia (Spiderwort)
This Spiderwort has been grown in our family gardens for four generations. Not sure of the exact taxonomic classification, but it is probably T. virginiana or a cross with T. ohiensis.
There are about 65 species of Tradescantia all native to the Americas, with T. virginiana and T. ohiensis found through most of eastern North America.
Primary bloom occurs May through July, and plants can be cut back to the ground as bloom diminishes. Cutting back will encourage attractive new foliage, and a late season rebloom.