Rock Springs is the source of the Rock Springs Run, a swift running stream with an average flow of 26.000 gallons per minute and a constant temperature of 68 degrees. The spring flows from limestone containing fossils that date back 17 million years. In 1855, the State of Florida, wanting to encourage settlement in the state's interior, awarded land near Rock Springs to William S. Delk, a veteran of the Second Seminole War. Delk later became the owner of the area's largest plantation. He used the Rock Springs Run to power his grist mill, sawmill, and cotton gin. Delk's heirs sold the land to lumber companies. In 1910, New Jersey doctor, Howard A. Kelly visited Rock Springs. Kelly, one of the founders of Johns Hopkins Hospital and an internationally recognized gynecologist, was an avid naturalist. Taken with the "sweet" spring water from the "mysterious cave," he purchased 200 acres around Rock Springs in 1921 for use as a wildlife preserve and bird sanctuary. Kelly and his wife gifted the land to Orange County in 1927 with the understanding that it would remain a public park open to every citizen. Orange County named the park Dr. Howard A. Kelly park.