Cronin was born in Greenwich, New York. He was a childhood friend of President Chester A. Arthur. After studying the arts in Troy, New York, he moved to New York City in 1855. He spent the years from 1857 in Europe, where he probably studied for one year at the Kunstakademie Düsseldorf. He is considered a member of the Düsseldorf school of painting. Cronin returned to the U.S. in 1860, joined the army and worked for Harper's Magazine.