 Born in Olympia, Washington, she was a child of General Thomas I. McKenny, who served as a General in the Civil War as well as Indian Agent for Washington Territory.Her mother was Cynthia Adelaide, and she was an only child.After attending local schools in Olympia, McKenny attended one of the few schools of landscape architecture open to women students at the turn of the century called the Lowthorpe School in Groton, Massachusetts.