Nestled beneath the San Jacinto Mountains in an oasis of palm trees is a mineral hot springs. For thousands of years, this was the winter home of the Agua Caliente Band of Cahuilla Indians, the original inhabitants of this harsh desert region. A U.S. government survey party discovered the spring in 1853 and identified the area located at the base of two bunches of palms. In 1884, Judge John McCallum of San Francisco purchased land near the springs for $800 and built the first adobe structure, which still stands today. Stage lines and railroads provided transportation through the area,...