Cornflower
Centaurea cyanus (Leucacantha cyanus)

Family: Sunflower (Asteraceae)
AKA: Bachelor's Button, Knapweed
Photo taken on: July 15, 2008
Location: Almont, CO
Life Zones: Plains to foothills
Habitat: Moist meadows

Grows to 2ft with leafy stems. It has escaped from cultivation to disturbed soil.

Flora of North America reference.