In 1960, the Mathis family moved to Coloma, another Mother Lode town, where they completely remodeled a Victorian-style house dating to the Gold Rush era (numerous photographs and sketches of the remodeling are housed in the archive). They named their restored home "Friday House," after Jean's maiden name. Here they both lived and operated an art gallery and studio, where they sold many products of lithography and George's numerous historical drawings and sketches. George Mathis became generally, and affectionately, known as the "pictorial historian of the Mother Lode.
Between 1959 and 1970, George Mathis' artistic career took a new course when he began work in Sacramento for the Aerojet Corporation, America's largest producer of rocket engines (Aeroject built the rocket engines for the Apollo and Gemini missions, as well as the Polaris, Delta, Titan, and Minuteman systems).
Mathis' work for Aeroject gained widespread exposure. At a time before computer graphics, his renderings of the Gemini and Apollo missions were broadcast on television and printed in newspapers and magazines.
Mathis often termed his work "engineering concepts" rather than "artist's concepts," since engineers studied his creations to visualize their proposed projects.
from articles on his published works.