Perched atop a mountain wilderness, the two mammoth solar tower telescopes and the 60- and 100-inch behemoth night-time reflectors of the Mount Wilson Observatory were the largest in the world, and at the center of the development of astrophysics. This book brings together the science and personal stories of those involved in the development of modern theories of stellar evolution and cosmology at the Mount Wilson Observatory. It is fully illustrated with contemporary photographs of people and instruments.