By 1925, the artist brothers Kenneth and William had joined forces to form "The Willmarths,". William and Kenneth began working for the Union Pacific Railroad in 1930, with covers for two Yellowstone National Park Union Pacific brochures. "In 1932 many railroads, including twelve in the West, held a poster contest to portray the beauty of the West and encourage summer travel. Many well-known artists were entered, and over fifty drawings were submitted. A committee of advertising agents of the Union Pacific, Southern Pacific, Northern Pacific, Santa Fe, and Burlington railroads made the judging in Chicago. William entered two watercolor sketches, Visit the Pacific Northwest Wonderland and New Mexico and Arizona Rockies, which were chosen among the first five winners." The pair also designed several posters for the Sun Valley Resort, as well as World War II "Keep 'em Rolling" posters for Union Pacific.