Pace was born on December 12, 1918, in Charleston, Missouri. Though he had started drawing as a child, he first received a sketchbook from a teacher when he was in the fourth grade. His parents, who had owned a farm and grocery store, moved to New Harmony, Indiana, when Pace was in his teens. His first formal training began when he was 17, when he studied anatomical studies and watercolor painting with Works Progress Administration artist Robert Lahr in Evansville, Indiana.

He served in the United States Army during World War II. He was injured while serving in Europe, and met Gertrude Stein and Pablo Picasso after being hospitalized in Paris. After completing his military service, Pace went to Mexico to study art under the G.I. Bill. While at a school in San Miguel de Allende, he met artist Milton Avery who convinced him to come to New York City to continue his education, learning there at the Art Students League of New York and independently with artist Hans Hofmann. (Source: Wikipedia).