Alexander Harmer was born in Newark, New Jersey. He is best known as a Western artist for depictions of the California missions, desert landscapes, Native American figures, and horses. As a young man, Harmer became intrigued by painting and began depicting scenes along the East coast. He studied art at the Pennsylvania School of Fine Arts in Philadelphia under Thomas Eakins and Thomas Anshutz. He also joined the army in and was stationed in California. It was here where he began his love of the West. In 1881 Harmer was assigned cavalry duty in Arizona, where his fought against Geronimo and the Apaches. Harmer became known as the “Artist of the Apaches” and made field sketches and notes to document the Apache tribe. Upon returning to the Pennsylvania Academy he began illustrating for Harper's Weekly and produced a series of oil paintings and watercolors on the subject.

In the 1890s, he moved to Santa Barbara, where he met his wife. He began painting scenes of early California history, portraying the period when Mexico held California. He often painted the California Missions. Harmer built his home and in an old adobe on De La Guerra Plaza. Harmer traveled throughout the world and exhibited extensively, Later, a number of artists, including Douglas Parshall, lived and worked in Alexander Harmer's old adobe studio in Santa Barbara, California.