Born in Kentucky, Ira Diamond Gerald Cassidy was raised in Cincinnati in a large family strongly influenced by the arts. Cassidy received his first training at the Institute of Mechanical Arts under Frank Duveneck (the noted teacher of a generation of U.S. artists including Joseph Sharp and Walter Ufer). He continued his studies at the Art Students League in New York and by his mid twenties was equipped with the skills with which to become a successful painter and lithographer.
Cassidy moved to Denver, finding it the perfect location to pursue parallel careers in commercial illustration and easel painting. Cassidy soon discovered his life's inspiration in the history, landscape and cultures of the West. In 1898 a severe case of pneumonia developed into a bout with tuberculosis. Cassidy moved to Albuquerque, known for its restorative environment, and soon was able to resume his painting. By 1912 he and his wife, noted author Ina Sizer Cassidy, settled in Santa Fe, becoming members of its beginning arts colony.
Cassidy is known for the flowing brushwork, distinctive compositions and clear, luminous colors of his paintings. He frequently sketched at the pueblos of the region, and his ability to capture both the action and spirit of his subjects led to many important mural and portrait commissions throughout the United States.
The artist's untimely death in 1934 tragically shortened a brilliant career. His graceful compositions of the Southwest are a timeless legacy.