Gilroy Hot Springs was discovered in the early 1860s by Mexican shepherd Francisco Cantua, then acquired by José Quintín Ortega and Ignacio María Ortega in 1865. Soon thereafter, George W. Roop purchased it and turned it into a destination mineral water resort. In its heyday up to 500 visitors per day enjoyed 5-Star dining, luxury hotel accommodations, outdoor and indoor activities including hunting, horseback riding, hiking, fishing, shuffleboard, croquet, music, dancing, parlor games, and more.

In the 1800s it was known to have the most healing waters in California. Civic leaders and business owners from the greater San Francisco Bay area and beyond were frequent visitors, including Spreckles, Marriott, Sutro, Sargent, and Phelan.