Early life and career
Hillerman was born in Denison, Texas, the son of Christopher Benedict Hillerman, a gas station owner, and Lenora Joan (née Medlinger). He was the middle child with two sisters. His father was the grandson of immigrants from Germany and France, and his mother the daughter of immigrants from Austria and Germany. Hillerman developed an interest in opera at the age of ten, and traveled to Dallas to watch Metropolitan Opera productions. He attended St. Xavier's Academy, and after graduation, he attended the University of Texas at Austin for three years, majoring in journalism.
Hillerman served four years in the United States Air Force (1953-1957), working in maintenance in a B-36 wing of the Strategic Air Command, and achieving the rank of sergeant. He became interested in acting after working with a theatrical group in Fort Worth during his service: "I was bored with barracks life. I got into [acting] to meet people in town. A light went on." After his 1957 discharge, he moved to New York City to study at the American Theatre Wing, and performed in professional theater for the next twelve years, in productions such as Henry IV, Part 2 and The Great God Brown. Despite over 100 stage roles, Hillerman was unable to make a living as a stage actor, and he moved to Hollywood in 1969.