aka widowsfrill; Silene stellata; Caryophyllaceae (pink family)
Starry campion is one of about 60 native and 18 alien species of Silene found in continental North America. It ranges throughout the eastern US except Maine and Florida, though it is no longer found in Vermont and Rhode Island, is of special concern in Connecticut, and is threatened in Michigan. The plant stands about one to two feet tall, with a terminal panicle of blossoms (and sometimes a few more panicles along the upper stem). It seems to like a variety of habitats, mostly in mesic soils on rocky slopes and along riverbanks, in light shade.
Another campion species I’ve found in the Carderock area is wild pink (Silene caroliniana), a low-growing plant of rocky places that blooms in early May: