Son of a builder, Ira Dymond Gerald Cassidy was born on November 10, 1869 and grew up in Cincinnati, Ohio. In Cincinatti he studied with painter Frank Duveneck at the Institute of Mechanical Arts when he was 12. By the time he was 20, he was art director with a New York City lithographer. Sticken by pneumonia which developed into TB in 1899, he entered a sanitarium in Albuquerque where he first painted the Southwest, changing his signature from Ira Diamond Cassidy to Gerald Cassidy. When he recovered sufficiently, he moved to Denver as a commercial artist and lithographer specializing in theatrical subjects. After returning briefly to New York City where he studied at the National Academy of Design and the Art Students League, he married Ina Sizer Davis and settled in Santa Fe, New Mexico in 1912, following Carlos Vierra (1904) and Kenneth Chapman (1909). He was also active in Los Angeles, California from 1913-1921.