Wilson was born in Chariton, Iowa in Lucas County, a rural area in the south-central portion of the state.
[1] In 1918, Wilson took a job as consulting editor for the National Academy of Music in New York City, where he remained until his death at the age of 55.
As a composer, Mortimer's European influenced late romantic style was similar to his contemporaries Henry Kimball Hadley and Frederick Shepherd Converse.
55 (1919) includes miniature musical portraits of William S. Hart, Charles Chaplin, Mary Pickford, Theda Bara (who is portrayed in an atonal, expressionistic style) and Douglas Fairbanks).
Mortimer was also the author of three books: The Rhetoric of Music (1907), Harmonic and Melodic Technical Studies (1908) and Orchestral Training (1921).