Philadelphia Fleabane - Erigeron philadelphicus

Also known as the Philadelphia Daisy.

Family: Sunflower Family (Compositae)
Aster Tribe: Astereae
Flowers: Flower head has "hundreds of fine filament-like ray flowers."
Plants: 8-28 inches tall, biennial or short-lived perennial.
Leaves: Spatula-like, clasping.

Sources

Identified by Lynn Fleming and Janet Wallace, and confirmed by consulting Kansas Wildflowers and Grasses.
Photo: Courtesy of S. Peregrine Johnson.