After a year he requested a discharge on grounds of being underage, working as a photographic assistant before enrolling at the Pennsylvania Academy of Fine Art in 1874.
Short of money, he again enlisted in the army in 1881, and was assigned to Troop L of the Sixth Cavalry at Fort Apache, Arizona.
The couple settled in the Abadie family residence, the Yorba-Abadie adobe, which under Alexander and Felicidad's patronage became an artists' colony.
He contributed illustrations to Harpers Weekly and other magazines, acquiring a reputation as a western artist, and as a leader of the California art community.
Their eldest son Alexander Bertrand ("Bert") Harmer (1896 – 1967) became a prominent Santa Barbara architect.