Aliases: Rocky Mountain Iris
Blooms: May - June
Western Blue Flag is very similar to Hartweg's Iris, but grows in wetter areas, can grow larger (up to two feet tall), and comes only in the purple variety pictured above.
Iris missouriensis etymology: Iris is named for the Greek goddess of the rainbow, a nod to the variety of flower colors found in the genus. Missouriensis is a reference to the state, which itself gets its name from the Missouri Indian tribe.   
This Photo: In Yosemite Valley, mid May