After serving in the United States Army in World War I, he attended the Chicago Academy of Fine Arts.

In Europe, he learned classical technique under the tutelage of artists who had studied under luminaries such as Monet, Sargent, and Degas.

Prior to WW2, Mosby was awarded a scholarship to The National Higher Institute of Fine Arts in Antwerp, Belgium.

He also did illustration work between 1927 and 1932 for such companies as Mars Candy, Portland Cement, Goodrich Tires, Chrysler, Pierce-Arrow, Dodge, Swift & Co. A mural by Mosby is in the St Matthew's Episcopal Church in Chicago.

[1] [2] Students Include : Richard Schmid, Gil Elvgren, Ted Smuskiewcz, Bill Parks, Howard Terpning, James J. Ingwersen and others.